This past weekend I set up my Windows 7 computer to record TV shows for free. Using an antenna. Actually, rabbit ears. Very old school! The picture is far superior to what I was getting via cable.
Want to know more? Here's a how-to:
Review the "Geek Your Rig" how-to from Microsoft. and the shopping list "Dave's look for less". http://windows.microsoft.com/en-us/Windows7/help/videos/geek-your-rig
If you don't have one already, you'll need either a good rooftop antenna, or the modern day equivalent of rabbit ears. Visit antennaweb.com to figure out the best option and where you need to point it. Radio Shack is the absolute best place to go for this. They will let you try one and return it for a different on if it doesn't work out. Sometimes you have to try several different ones to get the best reception.
I got this one at Radio Shack: http://www.radioshack.com/product/index.jsp?productId=3730720
My picture is far better than Comcast provided.
You will also need a coax to USB stick, which you can get at Fry's. Here's the manufacturer's website: http://www.pctvsystems.com/USHome/tabid/206/language/en-US/Default.aspx
This supports HDTV, which you'll be getting for free from now on over the air. Plug this baby in and wait. DON'T load their software, you don't need it. Just wait for Windows to find the device and download the right driver.
The easiest part is this. In windows 7 (and you'll need 7 or higher to do this), go to Start > Programs > Windows Media Center. Follow the instructions.
There is no step 5. Boom you are done.
Optional: Use an xbox360 as a streaming device: Go to apps > my apps > windows media center. Done. It will take it a while to grab your libraries from your pc.
I have some web info saved in a library here for more reading: http://pear.ly/brlHD