I have an ATI All-in-Wonder HD card (AIW), a combination TV Tuner Card and graphics card. Besides normal video card stuff, it can record over the air (OTA) and other signals. Yours MAY be just a tuner card.
It requires drivers - available at the ATI web site under tV tuners cards:
http://support.amd.com/us/gpudownload/Pages/index.aspx
Start with TV Tuner system and then continue through card model and Operating System.
Follow ATI instructions on how to remove old drivers and then install the new ones.
The tuner card requires TV inputs and software. I have an outdoor antenna that puts a coaxial cable feed into my AIW. I get great high-def signals, but obviously only for broadcast channels, about 20 in English. My cable provider, Comcast, now scrambles their signals and a cable box is required for their decoding. I opted NOT to limit my system to the one channel at a time that the box provides, so I never hooked up to that cable.
Software is needed to handle the tuner card activities. The card came with Catalyst Media Center. I found it failed often - losing channels and settings, so I quit using it. There are commercial programs, but I use NPVR, the successor to gbpvr:
http://forums.gbpvr.com//forumdisplay.php?10-NPVR-Announcements
In the software, you have to tell it to scan for channels, just like you have to do with a flat screen TV nowadays. Varies per software. Once the tuner/software recognize channels, you can then watch them.
My AIW card has two outputs: DVI and HDMI. I use the DVI for my computer monitor. I got a long HDMI cable (via the web - vastly cheaper) and it goes to my (larger) flat screen TV, so I can watch either recorded TV, live TV, or anything else from my computer on my larger TV screen. (Of course, the TV can also do live TV.) Works great, but none of it was painless or simple to do.
Good luck.
Rich