user32: Run the explorer process from the system directory.

dlls/user32/win.c

@@ -1785,6 +1785,7 @@ HWND WINAPI GetDesktopWindow(void)
             static const WCHAR command_line[] = {'\\','e','x','p','l','o','r','e','r','.','e','x','e',' ','/','d','e','s','k','t','o','p',0};
             STARTUPINFOW si;
             PROCESS_INFORMATION pi;
+            WCHAR systemdir[MAX_PATH];
             WCHAR cmdline[MAX_PATH + sizeof(command_line)/sizeof(WCHAR)];
 
             memset( &si, 0, sizeof(si) );
@@ -1794,10 +1795,11 @@ HWND WINAPI GetDesktopWindow(void)
             si.hStdOutput = 0;
             si.hStdError  = GetStdHandle( STD_ERROR_HANDLE );
 
-            GetSystemDirectoryW( cmdline, MAX_PATH );
+            GetSystemDirectoryW( systemdir, MAX_PATH );
+            lstrcpyW( cmdline, systemdir );
             lstrcatW( cmdline, command_line );
             if (CreateProcessW( NULL, cmdline, NULL, NULL, FALSE, DETACHED_PROCESS,
-                                NULL, NULL, &si, &pi ))
+                                NULL, systemdir, &si, &pi ))
             {
                 TRACE( "started explorer pid %04x tid %04x\n", pi.dwProcessId, pi.dwThreadId );
                 WaitForInputIdle( pi.hProcess, 10000 );