the first thing you want to do is determine what kind of signal you are going to record. analog cable = any analog TV tuner will work digital cable with a set top box = analog tuners can record it in analog, if you want HD then you want the Hauppauge HD-PVR. clear QAM(unencrypted digital cable) = Depending on the software you use, a tuner that is capable of Clear QAM. satellite/u-verse = they require a set top box, so it's just like digital cable. cablecard = Centon cablecard, I believe only Windows Media Center is certified to work with it. SageTV has a work around that interfaces WMC to record from it. over the air atsc = any ota HD tuner As far as software, you have Windows Media Center, SageTV, Beyond TV and some other free solutions. I suggest you just download the trial versions of the software and try it out yourself. Windows Media Center is pretty but it has some limitations and the hardcore users tend to use other solutions. Feel free to ask me any questions about PC based DVR's, I actually work for one of the companies and I'm pretty unbiased about the software.
There's a cool standalone network device called the Homerun from Silicon Dust that comes in single and dual tuner flavors. Check it out here. You can find them at Microcenter.
Yeah, you need what's called an IR blaster. They will run you around $40 and it works to perfection. I have one of those stupid comcast boxes (because Comcast is forcing all of its customers to go digital) and I have it synced up with the box. I also have an HD antenna connected into my WMC machine such that I can get the locals all in HD.
You have to use the receiver box in between the coaxial from the wall and the TV tuner card. In the Windows Media Center setup, you can tell it to use the guide from the cable company's listings. It then can change the channels on your cable box via the additional IR blaster cables it comes with. If you didn't have the cable company's receiver, I don't know how you would do it. http://windows.microsoft.com/en-US/...ot-problems-with-watching-TV-on-your-computer