ATI Radeon 7500 AIW does a perfect job with s-video input. Also can use ATI All in Wonder TV card (if don't want a new video card).
If you computer is not close to the Dish Receiver, just get a long S-video cable. I have used a 40 foot with not signal loss.
The ATI cards come with the software to capture the video in various codec's--MPEG1, MPEG2, etc.
Then once you have it captured on your computer hard disk, just burn to a CD-R., VCD, or DVD.
The ATI 7500 AIW also has S-out, so you can connect your computer to the TV and just play the video to the TV treating your PC as a PVR.
Once you get your PC, TV and PVR all connect for both input and output, you have an amazing system at your disposal.
I have a DVD, VCR, Dish 301 and Dish 501 all feeding into my computer. I use a Radio Shack switch to toggle between the various feeds. In addition I use the antenna in on the ATI card for OTA just case of bad weather. The ATI card gives you three inputs--S-video, comp, and antenna.