Thread: why the hell does this little bit of code make a difference? (windows message loop)

Here is my now working message loop, thanks to Hunter2's old space shooter game. I am using PeekMessage, and his little nifty Sleep() thingy which I don't understand:

Code:

while(!done)
	{
		DWORD start, timeElapsed;
		start = GetTickCount();

		while(PeekMessage(&Msg, NULL, 0, 0, PM_REMOVE))
		{
			TranslateMessage(&Msg);
			DispatchMessage(&Msg);
		}

		MainFunc(hWnd);

		timeElapsed = GetTickCount() - start;
		if(timeElapsed < FRAME_DELAY)
			Sleep(FRAME_DELAY - timeElapsed);
	}

if I don't have that if-statement in there, the timeElapsed one, it doesn't work good. if i keep it in it works great. could anyone explain what exactly that is doing?

lol im sure you could, Hunter