Yep, it's someone's modified version of a MS app. The ATOM MyRegisterClass(HINSTANCE hInstance) function has issues that MS would not introduce into any code. The function has a high probabilty of failure. This is totally unlike any MS tutorial I've ever seen.
Can someone help me, I'm trying to learn C?. Need I say more?
The mods should move this script kiddies post over to the Windows forum where it belongs.