Using XP - I actually paid for it

.
Must admit I quite like it, esp. with 2 Gb RAM and running in classic interface.
Until I got this new(er) PC I was using ME. I liked it a lot and had not one single problem with it. You just have to take out the garbage like System Restore etc. I ended up preferring it to 98SE.
I would go back to ME like a shot, but there are too many hardware issues involved (too much RAM, can't get drivers etc).
Awaiting XP SP3 (real soon now

) then will slipstream a new XP CD and take out most of the rubbish using nLite.
Vista - not likely, I'd rather use the dreaded L***x.