@Sadeememe - Could you please tell us which ATI TV Tuner card you have?
There are basically three types:
1) ATI TV Wonder - Only available in Pre-Built systems and requires a cablecard from your cable company.
2) ATI All-In-Wonder HD - This is a combination TV Tuner card and Graphics card built for Vista and Windows 7. It would only pick up over the air SD/HD channels and ClearQAM (unencrypted) channels from your cable provider.
3) ATI All-In-Wonder (non-HD) - This is the same as the All-In-Wonder HD (sans the over the air HD), but the product line was dropped before Vista/7 really came about. It will only function as a TV Tuner when installed into a system running Windows XP.