Change/Remove Program List

is there really a difference from regular windows and genuine?

Yes. The one with the WGA will have nothing but headaches from Microsoft ;D.

However, without it you can’t download & install Windows Updates via their website (but you still can via the Automatic Updates function in Windows) and you’ll be missing out on the Optional Updates.

On the other hand, if you lost the so-called genuine status you can get it back if you have to reinstall the WGA.