I am using WinXP Pro.
It runs really good.
Besides the fact it has WDM drivers,
I wanted WinXP Pro because it supports dual monitors and dual processors AND it is an UPDATE to Win 2000.
Lots of people say wait to upgrade to WinXP because of bugs but I haven't really seen much myself.
I didn't want to go from Win98se to Win 2000 THEN to WinXP Pro.
As far as going to WinXP Home edition, I don't know about the other differences besides the two above.
And as far as the continual upgrading process goes,
Watch Out!
After getting WinXP Pro on the day it came out, I wanted to get a dual monitor video card, with no intention of getting new dual 19 inch monitors right away...
Well 5 thousand dollars later, I have bought lots of stuff for my studio.
You should stop and think about what your goals are as far as music goes, then you can make the right decisions on what to upgrade or buy next.
Although I have NO regrets about buying all this stuff
($800.00 microphone?), it did happen pretty fast as I was caught up in it. Just know where you want to go, and the rest will take care of itself.
Good luck and the most important thing to do is,
Keep On Making Music!
A1MixMan