I just found out windows 2000 breaking a small part of my codes. It used to work in Windows 98. Here is the snipper of the codes that didn''t work char strFileName[255]; ::ZeroMemory( strFileName, sizeof( strFileName ) ); GetModuleFileName( NULL, strFileName, sizeof( strFileName ) ); // create mutex, if succeeded means only instance HANDLE hMutex = ::CreateMutex( NULL, TRUE, strFileName ); if ( ::GetLastError() == ERROR_ALREADY_EXISTS ) { ::CloseHandle( hMutex ); // jump to previous game instance HWND hWnd = ::FindWindowEx( NULL, NULL, GFC_GameUtils::getWindowClassName(), NULL ); if ( hWnd ) { ::ShowWindow( hWnd, SW_RESTORE ); ::BringWindowToTop( hWnd ); ::SetForegroundWindow( hWnd ); } return false; } return true; When I ran this application in Windows 98, it worked(I had only 1 instance running max, and second instances sets focus to the first instance. However, in Windows 2000, i can get multiple application instances. Anyway can explain why?

The mutex name is invalid. (i.e. C:\MyProgram\MyProgram.exe)

Check the documentation for ::CreateMutex. It supports new prefixes "Global\" and "Local\" on 2000. Also, it specifically states that backslashes are not valid characters for the NT and 9x platforms. (Why it worked, I don''t know.)

Tim

The following code snipper hops to the previous game instance
// jump to previous game instance
HWND hWnd = ::FindWindowEx( NULL, NULL, GFC_GameUtils::getWindowClassName(), NULL );
if ( hWnd ) {
::ShowWindow( hWnd, SW_RESTORE );
::BringWindowToTop( hWnd );
::SetForegroundWindow( hWnd );
}