Using Media Center under the following conditions was resulting in stuttering video and audio, and the occasional green screen:

• Windows Vista Ultimate SP1, 64-bit
• 4 GB RAM
• NVidia GeForce 8800 GTS
• Hauppauge WinTV 1600 TV Tuner

I've seen a lot of posts on message boards where people are experiencing similar issues, all with strange suggestions that don't seem to work. I accidentally discovered my own solution, which I hope helps anyone else with the same problem.

Here's what I did:

1. Go to Hauppauge's website and download the newest drivers
2. Extract the contents of the zip file
3. Run hcwclear.exe, selecting the Remove All WinTV Drivers and Applications (Total Removal) and Search All .INF Files for Conflicting Hardware options
4. Reboot
5. When Windows discovers new hardware after rebooting, allow it to look for new drivers

I have seen other instructions that indicate you should use the downloaded drivers, but in my case, the drivers available through Windows Update worked fine.