IamDavid- no, I only use PowerDVD these days. I used to use WinDVD8, but I didn't like the interface of it. But the UVD acceleration is working, because if I use my onboard video GeForce 6100, which has no acceleration for HD, the CPU is at 100% and it's dropping frames a lot.
Also, I'm sure the Ubuntu will run just fine, I have Ubuntu installed on Pentium3 # 866MHZ, o/c to 910Mhz, 256MB DDR133 ad GeForce4, runs perfectly fine, but a little slow. Actually, it has problems running video 720*480, but if I add my Audigy 2 ZS, it runs the video just fine. It seems the onboard audio is just not accelerating anything.
Good luck with your project!