Hoow to record shows

hi tomshardware community,
I built my own computer about year ago, and now I want to record tv shows on my pc. I am pretty computer literate, but all I know is that I need a tv tuner card. Do you guys have any suggestions on which one? and can I do this with directv or cable only? If it helps here is my system:

PS: Generic 350W
Mobo: MSI K8N Neo
CPU: AMD Athlon 64 2800+
RAM: 1 GB DDR333
Video card: eVGA FX 5500 256MB Vid Ram
Hard Drive: Western Digital 80GB

If you guys need any other info just ask.
Thanks

DirectTV is a satelite provider, like bell express vu and dish network

and sorry but I have almost no idea how to work with tuner cards

There are some digital cards available already. But just one piece of advice. NEVER buy a card from pinnacle. NEVER. They generally only work with pinnacle software and you don't want that piece of crap infesting your computer.

Go for Hauppage for example.

Correct that digital cards are hard to come by but you can keep your decoder box in the line and use the output from the box into your tuner card using composite video. This should give you decent quality.

Yeah you can just keep the cable box in the loop and record from the cable box. The quality would be the same as the quality of it on your TV. You can also get HDTV tuner cards if you want to record stuff like the Simpsons off of Fox's HD channel (available here at least). But the signal isn't going to be better than whats actually being broadcasted. Most channels are still 720x480 in the US so thats what you'll record at off the cable box.