Win7 on my desktop and XP on my eee. I also have a laptop with a linux distro on it, but after installing it I haven't even booted the thing (I know it's definitely not running ubuntu).
I m happy with windows Vista....... In my Laptop. Its going good and its security options are really awesome.
windows 7 ultimate on 4 machines, have win xp on 1, red hat linux on 1 have 24 licensed copies still unused for office, for windows 7 ultimate (8) pro(16)
On my laptop I am using Windows Vista and on my desktop I am using windows XP. I think windows XP is the best version of the windows