I have an optiplex GX260, P4 2.4, 2GB Ram, FX5200 video card and a Hauppauge 1600 tuner card.

This machine cannot handle HDTV OTA using Windows Media Center 2005. It's spits and sputters terrible. I was wondering if I'd have better luck installing Ubuntu and loading something like MythTV. Or would I be wasting my time?

My first HTPC was a P4 3.0, 1GB ram and FX5200 video. With the nvidia drivers, debian linux, and mplayer I never had a problem with smooth playback. I cannot comment on your tuner card.

I don't think the 5200 can handle HD.

THe FX5200 can handle HD just fine- on Linux, the CPU is the limiting factor.

In your case, the 2.4Ghz CPU should be sufficient for ATSC/QAM MPEG2 720p and 1080i.

VC1 is probably doable, and maybe 720p x/h264, but not 1080p x/h264. But for the OTA HD stuff, you shouldn't have a problem.

I have an old MX440 that is doing ATSC just fine. It is my CPU that was causing stutters. It's a 2.4 celeron. When overclocked to 3gig, I get smooth HDTV even with the MX440.

But, no, Linux doesn't really use any less resources than Windows, in my experience.

I have an old MX440 as well that displays HD just fine, with P4 2.6 CPU. So it's worth a try. You may want to cut down on concurrent processes. When I have a few programs running at the same time, I get stutters...

Did you have to tweak xorg options to get the 5200 to 1920x1080, rgb? Just wondering, because I had to with my 8500GT.

With proper settings it should work fine. I used an old Duron 1600 clocked down to 1200MHz (12x100) 512M with an FX5200 and XvMC and could get smooth playback (except when OSD was up). Clocked at 2GHz (12x166), it worked fine without XvMC at about 80% cpu load.