WHY am I now having problems with syncing audio and visual?

HI,

Downloaded version 7 of Nero premium and nothing I download (movies, no matter what type, AVI, etc) produces a sync between the audio and visual. No problems before this, just now. I have to revert to using Windows Media Player to play anything on the computer and as for burning to CD or DVD, well that is out of sync too given that Nero just isn’t syncing it in the first place! What could be the reason for this? I downloaded Nero from a torrent website, input the serial number and it never syncs audio and visual. Other people appear to be doing ok according to the feedback on the torrent website.

ANY HELP OR IDEAS WOULD BE GREATLY APPRECIATED!

Cheers
Oz12