Sorry, I didn't see you'd already uninstalled and reinstalled, my bad.
Good to hear it worked with no lag for you, I haven't had time to try it on my new PC yet but my older one lagged at the end of each level, really badly. Maybe just my own bad experience.
The Windows Live experiences I had related to Halo 2, I haven't even attempted getting Gears online yet because Halo 2 daunted me so much. The only two reasons I installed Vista were Halo 2, and Crysis in DX10. Crysis was barely playable in Vista and Halo 2 wouldn't even work - hence the reason I'm now Vista-less.