If you can run other software and play files, then your soundcard is fine. You can try to uninstall the software
and delete the directory left over in \Program Files, then re-install iTunes.
If you can't play audio files, try and see if there are any driver updates available for your soundcard.
Update:
This is a KB article right from the Apple website with regards to your problem. Make sure when you uninstall iTunes, that you uninstall QuickTime as well.
iTunes 7 for Windows: iTunes has detected an audio configuration problem