ixion: Removing, testing, RMA'ing, and then installing a replacement drive take longer than restoring from backup. At least for me -- YMMV.
Also, I didn't catch that this would be serving your whole house. Only ~2 rooms rely on my PCs for TV.
Why would a hardware raid card not be good enough for to support simultaneous HD captures?
Capturing 3 15MB/s streams is a lot harder for a disk system than one 45MB/s stream. Even one with 100MB/s of peak write capability might not handle it unless it can intelligently spread out the I/O. That takes an expensive hardware card. I don't know how smart software RAID has gotten, but I doubt something equal to Areca/3ware/LSI is available yet, at least on the Windows platform.
Then again, the streams y'all are talking about aren't too taxing. Anything that's HD, despite the extra pixels, will be already compressed over the wire down to 4MB/s or less. That's a lot easier to handle than the analog capture I'm used to.
it sounds like most of you feel RAID isn't such a good idea on a home PC - i have RAID 1 on my system. is there an easy way to get rid of it - or - am i stuck with it?
RAID 1 is fine. If you don't know how to change it then you probably shouldn't mess with it...
OS file rarely have writes to them except for page files, and if your paging much especially on a HTPC you don't have enough ram.
On a vanilla WinXP HTPC, maybe. On normal machines there's the indexing service, Outlook, Foldershare, compilers, etc...no matter how many 10K RPM spindles I throw at it, it seems it's always the bottleneck.