When I try the code in the book "Programming Windows" by Charles Petzold, I always can't quit from the program properly.

I used the code like this:
Code:
	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
to quit. The window can be closed every time, but there still a process left in Windows. Then next time, when I want to compile it and run again, the VC6 will give out an error.

What makes this happen? Thank you in advance!