diff --git a/source/graphics/tests/test_MeshManager.h b/source/graphics/tests/test_MeshManager.h
index 3f21e59130..554292f86d 100644
--- a/source/graphics/tests/test_MeshManager.h
+++ b/source/graphics/tests/test_MeshManager.h
@@ -28,8 +28,8 @@
 #include "ps/CLogger.h"
 #include "ps/Pyrogenesis.h"
 
-static fs::path MOD_PATH(psLogPath()/"../data/mods/_test.mesh");
-static fs::path CACHE_PATH(psLogPath()/"../data/_testcache");
+static fs::path MOD_PATH(fs::path(psLogDir())/"../data/mods/_test.mesh");
+static fs::path CACHE_PATH(fs::path(psLogDir())/"../data/_testcache");
 
 const char* srcDAE = "collada/sphere.dae";
 const char* srcPMD = "collada/sphere.pmd";
diff --git a/source/lib/file/vfs/vfs.cpp b/source/lib/file/vfs/vfs.cpp
index d15be6240b..3730af6157 100644
--- a/source/lib/file/vfs/vfs.cpp
+++ b/source/lib/file/vfs/vfs.cpp
@@ -42,7 +42,7 @@ public:
 	virtual LibError Mount(const VfsPath& mountPoint, const fs::path& path, size_t flags /* = 0 */, size_t priority /* = 0 */)
 	{
 		debug_assert(vfs_path_IsDirectory(mountPoint));
-		// note: mounting subdirectories is now allowed.
+		fs::create_directories(path);
 
 		VfsDirectory* directory;
 		CHECK_ERR(vfs_Lookup(mountPoint, &m_rootDirectory, directory, 0, VFS_LOOKUP_ADD|VFS_LOOKUP_CREATE));
diff --git a/source/lib/sysdep/os/win/wutil.cpp b/source/lib/sysdep/os/win/wutil.cpp
index 6f23432272..0930106314 100644
--- a/source/lib/sysdep/os/win/wutil.cpp
+++ b/source/lib/sysdep/os/win/wutil.cpp
@@ -30,6 +30,9 @@
 #include "win.h"
 #include "winit.h"
 
+#include <shlobj.h>	// SHGetFolderPath
+
+
 WINIT_REGISTER_EARLY_INIT(wutil_Init);
 WINIT_REGISTER_LATE_SHUTDOWN(wutil_Shutdown);
 
@@ -232,19 +235,37 @@ bool wutil_HasCommandLineArgument(const char* arg)
 
 char win_sys_dir[MAX_PATH+1];
 char win_exe_dir[MAX_PATH+1];
+char win_appdata_dir[MAX_PATH+1];
 
 static void GetDirectories()
 {
-	GetSystemDirectory(win_sys_dir, sizeof(win_sys_dir));
+	WinScopedPreserveLastError s;
 
-	const DWORD len = GetModuleFileName(GetModuleHandle(0), win_exe_dir, MAX_PATH);
-	debug_assert(len != 0);
-	// strip EXE filename and trailing slash
-	char* slash = strrchr(win_exe_dir, '\\');
-	if(slash)
-		*slash = '\0';
-	else
-		debug_assert(0);	// directory name invalid?!
+	// system directory
+	{
+		const UINT charsWritten = GetSystemDirectory(win_sys_dir, ARRAY_SIZE(win_sys_dir));
+		debug_assert(charsWritten != 0);
+	}
+
+	// executable's directory
+	{
+		const DWORD len = GetModuleFileName(GetModuleHandle(0), win_exe_dir, ARRAY_SIZE(win_exe_dir));
+		debug_assert(len != 0);
+		// strip EXE filename and trailing slash
+		char* slash = strrchr(win_exe_dir, '\\');
+		if(slash)
+			*slash = '\0';
+		else
+			debug_assert(0);	// directory name invalid?!
+	}
+
+	// application data
+	{
+		HWND hwnd = 0;	// ignored unless a dial-up connection is needed to access the folder
+		HANDLE token = 0;
+		const HRESULT ret = SHGetFolderPath(hwnd, CSIDL_APPDATA, token, 0, win_appdata_dir);
+		debug_assert(SUCCEEDED(ret));
+	}
 }
 
 
diff --git a/source/lib/sysdep/os/win/wutil.h b/source/lib/sysdep/os/win/wutil.h
index c97e312c71..262028516e 100644
--- a/source/lib/sysdep/os/win/wutil.h
+++ b/source/lib/sysdep/os/win/wutil.h
@@ -99,6 +99,7 @@ public:
 	WinScopedPreserveLastError()
 		: m_lastError(GetLastError())
 	{
+		SetLastError(0);
 	}
 	
 	~WinScopedPreserveLastError()
@@ -143,9 +144,10 @@ extern bool wutil_HasCommandLineArgument(const char* arg);
 // directories
 //
 
-// neither of these end in a slash.
+// none of these end with a slash.
 extern char win_sys_dir[MAX_PATH+1];
 extern char win_exe_dir[MAX_PATH+1];
+extern char win_appdata_dir[MAX_PATH+1];
 
 
 //
diff --git a/source/network/NetLog.cpp b/source/network/NetLog.cpp
index c8cb50ef61..9f83eff994 100644
--- a/source/network/NetLog.cpp
+++ b/source/network/NetLog.cpp
@@ -258,7 +258,7 @@ CNetLogFileSink::CNetLogFileSink( void )
 	CNetLogger::GetStringTime( time );
 	
 	// Make relative path
-	fs::path path(psLogPath()/"net_log");
+	fs::path path(fs::path(psLogDir())/"net_log");
 	path /= time+".txt";
 	m_FileName = path.external_file_string();
 	m_Append = true;
diff --git a/source/ps/CLogger.cpp b/source/ps/CLogger.cpp
index 18eee81adf..4f0a39ab26 100644
--- a/source/ps/CLogger.cpp
+++ b/source/ps/CLogger.cpp
@@ -54,10 +54,10 @@ const char* html_footer = "";
 
 CLogger::CLogger()
 {
-	fs::path mainlogPath(psLogPath()/"mainlog.html");
+	fs::path mainlogPath(fs::path(psLogDir())/"mainlog.html");
 	m_MainLog = new std::ofstream(mainlogPath.external_file_string().c_str(), std::ofstream::out | std::ofstream::trunc);
 
-	fs::path interestinglogPath(psLogPath()/"interestinglog.html");
+	fs::path interestinglogPath(fs::path(psLogDir())/"interestinglog.html");
 	m_InterestingLog = new std::ofstream(interestinglogPath.external_file_string().c_str(), std::ofstream::out | std::ofstream::trunc);
 
 	m_OwnsStreams = true;
diff --git a/source/ps/ConfigDB.cpp b/source/ps/ConfigDB.cpp
index 27693bcba6..372ed39b80 100644
--- a/source/ps/ConfigDB.cpp
+++ b/source/ps/ConfigDB.cpp
@@ -274,7 +274,7 @@ bool CConfigDB::Reload(EConfigNamespace ns)
 	shared_ptr<u8> buffer; size_t buflen;
 	{
 		// Handle missing files quietly
-		if (g_VFS->GetFileInfo(m_ConfigFile[ns], NULL) == ERR::VFS_FILE_NOT_FOUND)
+		if (g_VFS->GetFileInfo(m_ConfigFile[ns], NULL) < 0)
 		{
 			LOG(CLogger::Warning, LOG_CATEGORY, "Cannot find config file \"%s\" - ignoring", m_ConfigFile[ns].c_str());
 			return false;
diff --git a/source/ps/GameSetup/GameSetup.cpp b/source/ps/GameSetup/GameSetup.cpp
index 7365bbdec1..cc87896194 100644
--- a/source/ps/GameSetup/GameSetup.cpp
+++ b/source/ps/GameSetup/GameSetup.cpp
@@ -17,6 +17,9 @@
 
 #include "precompiled.h"
 
+#if OS_WIN
+#include "lib/sysdep/os/win/wutil.h"
+#endif
 #include "lib/external_libraries/sdl.h"
 #include "lib/ogl.h"
 #include "lib/timer.h"
@@ -88,6 +91,7 @@
 #include "network/NetServer.h"
 #include "network/NetClient.h"
 
+#include "ps/Pyrogenesis.h"	// psSetLogDir
 #include "ps/GameSetup/Atlas.h"
 #include "ps/GameSetup/GameSetup.h"
 #include "ps/GameSetup/Config.h"
@@ -551,63 +555,154 @@ static size_t ChooseCacheSize()
 	return 96*MiB;
 }
 
-fs::path BinariesDir(const CStr& argv0)
+
+class Paths
 {
-	// get full path to executable
-	char pathname[PATH_MAX];
-	// .. first try safe, but system-dependent version
-	if(sys_get_executable_name(pathname, PATH_MAX) < 0)
+public:
+	Paths(const CStr& argv0, const char* subdirectoryName)
 	{
-		// .. failed; use argv[0]
-		errno = 0;
-		if(!realpath(argv0.c_str(), pathname))
-			WARN_ERR(LibError_from_errno(false));
+		m_root = Root(argv0);
+		m_rdata = m_root/"data";
+
+		// everything is a subdirectory of the root
+		if(!subdirectoryName)
+		{
+			m_data = m_rdata;
+			m_config = m_data/"config";
+			m_cache = m_data/"cache";
+			m_logs = m_root/"logs";
+		}
+		else
+		{
+#if OS_WIN
+			const fs::path appdata(fs::path(win_appdata_dir)/subdirectoryName);
+			m_data = appdata/"data";
+			m_config = appdata/"config";
+			m_cache = appdata/"cache";
+			m_logs = appdata/"logs";
+#else
+			const char* envHome = getenv("HOME");
+			debug_assert(envHome);
+			const fs::path home(envHome);
+			m_data = XDG_Path("XDG_DATA_HOME", home/".local/share")/subdirectoryName;
+			m_config = XDG_Path("XDG_CONFIG_HOME", home/".config")/subdirectoryName;
+			m_cache = XDG_Path("XDG_CACHE_HOME", home/".cache")/subdirectoryName;
+			m_logs = m_config/"logs";
+#endif
+		}
 	}
 
-	// make sure it's valid
-	errno = 0;
-	if(access(pathname, X_OK) < 0)
-		WARN_ERR(LibError_from_errno(false));
+	const fs::path& Root() const
+	{
+		return m_root;
+	}
 
-	// strip executable name
-	char* name = (char*)path_name_only(pathname);
-	*name = '\0';
+	const fs::path& RData() const
+	{
+		return m_rdata;
+	}
 
-	return fs::path(pathname);
-}
+	const fs::path& Data() const
+	{
+		return m_data;
+	}
+
+	const fs::path& Config() const
+	{
+		return m_config;
+	}
+
+	const fs::path& Cache() const
+	{
+		return m_cache;
+	}
+
+	const fs::path& Logs() const
+	{
+		return m_logs;
+	}
+
+private:
+	static fs::path Root(const CStr& argv0)
+	{
+		// get full path to executable
+		char pathname[PATH_MAX];
+		// .. first try safe, but system-dependent version
+		if(sys_get_executable_name(pathname, PATH_MAX) < 0)
+		{
+			// .. failed; use argv[0]
+			errno = 0;
+			if(!realpath(argv0.c_str(), pathname))
+				WARN_ERR(LibError_from_errno(false));
+		}
+
+		// make sure it's valid
+		errno = 0;
+		if(access(pathname, X_OK) < 0)
+			WARN_ERR(LibError_from_errno(false));
+
+		fs::path path(pathname);
+		for(size_t i = 0; i < 3; i++)	// remove "system/name.exe"
+			path.remove_leaf();
+		return path;
+	}
+
+	static fs::path XDG_Path(const char* envname, const fs::path& home, const fs::path& defaultPath)
+	{
+		const char* path = getenv(envname);
+		if(path)
+		{
+			if(path[0] != '/')	// relative to $HOME
+				return home/path;
+			return fs::path(path);
+		}
+		return defaultPath;
+	}
+
+	// read-only directories, fixed paths relative to executable
+	fs::path m_root;
+	fs::path m_rdata;
+
+	// writable directories
+	fs::path m_data;
+	fs::path m_config;
+	fs::path m_cache;
+	fs::path m_logs;	// special-cased in single-root-folder installations
+};
 
 
 static void InitVfs(const CmdLineArgs& args)
 {
 	TIMER("InitVfs");
 
+	const char* subdirectory = args.Has("writableRoot")? 0 : "0ad";
+	const Paths paths(args.GetArg0(), subdirectory);
+
+	fs::path logs(paths.Logs());
+	fs::create_directories(logs);
+	psSetLogDir(logs.string().c_str());
+
 	const size_t cacheSize = ChooseCacheSize();
 	g_VFS = CreateVfs(cacheSize);
 
-	const fs::path binariesDir(BinariesDir(args.GetArg0()));
-	g_VFS->Mount("screenshots/", binariesDir/"../data/screenshots");
-	g_VFS->Mount("config/", binariesDir/"../data/config");
-	g_VFS->Mount("profiles/", binariesDir/"../data/profiles");
-
-	// rationale:
-	// - this is in a separate real directory so that it can later be moved
-	//   to $APPDATA to allow running without Admin access.
-	// - we mount as archivable so that all files will be added to archive.
-	//   even though we write out XMBs here, they will eventually be read,
-	//   so putting them in an archive boosts performance.
-	g_VFS->Mount("cache/", binariesDir/"../data/cache", VFS_MOUNT_ARCHIVABLE);
+	g_VFS->Mount("screenshots/", paths.Data()/"screenshots");
+	g_VFS->Mount("config/", paths.RData()/"config");
+	g_VFS->Mount("profiles/", paths.Config()/"profiles");
+	g_VFS->Mount("cache/", paths.Cache(), VFS_MOUNT_ARCHIVABLE);	// (adding XMBs to archive speeds up subsequent reads)
 
 	std::vector<CStr> mods = args.GetMultiple("mod");
 	mods.push_back("public");
 	if(!args.Has("onlyPublicFiles"))
 		mods.push_back("internal");
 
+	fs::path modArchivePath(paths.Cache()/"mods");
+	fs::path modLoosePath(paths.RData()/"mods");
 	for (size_t i = 0; i < mods.size(); ++i)
 	{
-		CStr path = "mods/" + mods[i];
 		size_t priority = i;
 		const int flags = VFS_MOUNT_WATCH|VFS_MOUNT_ARCHIVABLE;
-		g_VFS->Mount("", (binariesDir/"../data")/path, flags, priority);
+		g_VFS->Mount("", modLoosePath/mods[i], flags, priority);
+		g_VFS->Mount("", modArchivePath/mods[i], flags, priority);
 	}
 
 	// don't try g_VFS->Display yet: SDL_Init hasn't yet redirected stdout
@@ -916,7 +1011,7 @@ void Init(const CmdLineArgs& args, int flags)
 	hooks.translate = psTranslate;
 	hooks.translate_free = psTranslateFree;
 	hooks.bundle_logs = psBundleLogs;
-	hooks.get_log_dir = psGetLogDir;
+	hooks.get_log_dir = psLogDir;
 	app_hooks_update(&hooks);
 
 	// Set up the console early, so that debugging
diff --git a/source/ps/ProfileViewer.cpp b/source/ps/ProfileViewer.cpp
index 7e07d506af..4df93a5c36 100644
--- a/source/ps/ProfileViewer.cpp
+++ b/source/ps/ProfileViewer.cpp
@@ -428,7 +428,7 @@ void CProfileViewer::SaveToFile()
 	{
 		// Open the file. (It will be closed when the CProfileViewer
 		// destructor is called.)
-		fs::path path(psLogPath()/"profile.txt");
+		fs::path path(fs::path(psLogDir())/"profile.txt");
 		m->outputStream.open(path.external_file_string().c_str(), std::ofstream::out | std::ofstream::trunc);
 
 		if (m->outputStream.fail())
diff --git a/source/ps/Pyrogenesis.cpp b/source/ps/Pyrogenesis.cpp
index 55c40bc7af..e533a91dfd 100644
--- a/source/ps/Pyrogenesis.cpp
+++ b/source/ps/Pyrogenesis.cpp
@@ -93,35 +93,25 @@ void psBundleLogs(FILE* f)
 	fwprintf(f, L"SVN Revision: %s\n\n", svn_revision);
 
 	fwprintf(f, L"System info:\n\n");
-	fs::path path1(psLogPath()/"system_info.txt");
+	fs::path path1(fs::path(psLogDir())/"system_info.txt");
 	AppendAsciiFile(f, path1.external_file_string().c_str());
 	fwprintf(f, L"\n\n====================================\n\n");
 
 	fwprintf(f, L"Main log:\n\n");
-	fs::path path2(psLogPath()/"mainlog.html");
+	fs::path path2(fs::path(psLogDir())/"mainlog.html");
 	AppendAsciiFile(f, path2.external_file_string().c_str());
 	fwprintf(f, L"\n\n====================================\n\n");
 }
 
 
-const char* psGetLogDir()
+static char logDir[PATH_MAX];
+
+void psSetLogDir(const char* path)
 {
-	static char N_log_dir[PATH_MAX];
-	ONCE(\
-		char N_exe_name[PATH_MAX];\
-		(void)sys_get_executable_name(N_exe_name, ARRAY_SIZE(N_exe_name));\
-		/* strip app name (we only want its path) */\
-		path_strip_fn(N_exe_name);\
-		(void)path_append(N_log_dir, N_exe_name, "../logs/");
-	);
-	return N_log_dir;
+	path_copy(logDir, path);
 }
 
-
-fs::path psLogPath()
+const char* psLogDir()
 {
-	char exePathname[PATH_MAX];
-	(void)sys_get_executable_name(exePathname, ARRAY_SIZE(exePathname));
-	path_strip_fn(exePathname);
-	return fs::path(exePathname)/"../logs/";
+	return logDir;
 }
diff --git a/source/ps/Pyrogenesis.h b/source/ps/Pyrogenesis.h
index e9a7983eac..6c3b56732e 100644
--- a/source/ps/Pyrogenesis.h
+++ b/source/ps/Pyrogenesis.h
@@ -42,11 +42,7 @@ extern const wchar_t* psTranslate(const wchar_t* text);
 extern void psTranslateFree(const wchar_t* text);
 extern void psBundleLogs(FILE* f);
 
-// (this is used by AppHooks during crash reporting, where it's useful
-// not to allocate any memory.)
-extern const char* psGetLogDir();
-
-// same as psGetLogDir, but more convenient (yet doesn't cache the results).
-extern fs::path psLogPath();
+extern void psSetLogDir(const char* path);	// set during InitVfs
+extern const char* psLogDir();	// used by AppHooks and engine code when reporting errors
 
 #endif
diff --git a/source/ps/Util.cpp b/source/ps/Util.cpp
index ea9869a539..5e7820c4c0 100644
--- a/source/ps/Util.cpp
+++ b/source/ps/Util.cpp
@@ -71,7 +71,7 @@ void WriteSystemInfo()
 	struct utsname un;
 	uname(&un);
 
-	fs::path pathname(psLogPath()/"system_info.txt");
+	fs::path pathname(fs::path(psLogDir())/"system_info.txt");
 	FILE* f = fopen(pathname.external_file_string().c_str(), "w");
 	if(!f)
 		return;