i use 2003 often. it is fast than xp b/c because the new kernal.. xp pose to have a updated kernal with sp2 next year...
but 2003 is faster, plus very stable.
not all apps work under 2003 just to let you know.. my mains work though..Nuendo 2.1, wavelab 4, a bunch of plugs, delta 1010 w/xp drivers...
a lot of sonic foundry/sony stuff doesn't work with 2003.