I do use my computer as a TiVo, but I have cable, not satellite. However, the recording software I use, BeyondTV, has a support forum where I often see people mention their satellite setups. I never pay much attention to how it is set up, because it never really mattered to me, but you could look into it and see how they are getting it to work possibly. A search through the knowledge base and discussion forums over at
www.snapstream.com couldn't hurt, in any case.
I'm not saying you'll need to buy the software (though it is one hell of a program, as I can atest), but maybe you can get some ideas into how to put together your own recording solution from what other people have done.