If I build a HTPC, is there any software that would create the video files in a format that I could watch them on my (not at the moment) network connected TiVo or visa versa?
Well, you'd have to hack the Tivo, but the tivo itself resords in mpeg2. Tying this into John's question about hardware...
The Hauppauge 250 is tuner/capture card of choice by many HTPCers as it uses hardware to encode the data to mpeg (versus, say a AIW, which uses software) thus taking a lot of pressure off the CPU. The only downside is that is ONLY records in mpeg format, so you would have to transcode it if you wanted it in a nother format (the AIW can record in WMA format).
Most programs support the pvr-250 cards (if they don't... they aren't worth the time to look at 'em), so with a little hacking you could stream shows that you saved with your HTPC to a tivo box. I have read that Tivo may be coming out with an option that would allow users to save shows to their networked PCs, but who know if and when that will happen.
If you only want to display to a standard def. tv, you can easily get away with a 1.7Ghz machine (possible as low as a 1.2) using a pvr-250 (they sell for a little over $100) and a GF5200 (about $50) vid card. You dont need a top of the line computer. Better yet, if you make a media server, you could use a total pos CPU (around 500mhz?) with multiple pvr-250s and a raid-5. Then use something like the Hauppauge MVP player to stream it to your tv. So many ways to work it.
Now if want to display it on a HDTV... well, you may want a higher CPU machine (over 2.8Ghz), so you can use FFDShow (a post processing program) that will really enhance all your video media.
Front ends... well, thats another thread all together, but a popular one would be Meedio. There are a lot of choices and its hard to know which one will work best for anyone else's situation. Since I'll be recieving the Planar 12" touchscreen soon, I have been looking into Netremote, MediaPortal, Xlobby, and Meedio as they fit my budget a little better than some of the higher end ones. So far Netremote has peaked most of my interest as I dont need an integrated tv player, it works with girder (intimately), and JohnWPB did some kickin' screens using NR on his 12" TS which really got me, well.... drooling
Sorry for the ramblin'
Treetop