I was using XP up to about 6 month ago. Vista was horrible when it first came out, but I have to say that now with SP1 and better drivers, Vista x64 runs really really well on my Q6600 w/ 4GB Ram. I'm dual booting my Vista and Win 7 RC, but I think I just need a few days to update my stuff and I'll probably only windows 7. Btw, those who notice the bad quality of h264 on Win 7 in MPC and VLC (it's really much better in Vista), try divx 7.0, it works great at much better quality. And dont mess with an old deamon tools or you might face a reinstall.