I want to know where the hell is the program call registry in the computer

DON'T TOUCH IT !!!!

The Registry controls everything within a Windows system!!

The Window's registry is a "virtual" database, that is created from multiple files. To view it, use the regedit application: Start -> Run -> regedit -> Enter.

As mentioned by Curlyben, the registry in Windows is not something to mess about with, especially if you have limited technical knowledge. If you have to fiddle, then back it up first: File -> Export -> Save.