what do you mean swap? If your instaling XP nope, but a fresh install won't keep your settings and programs as im sure you know, you can keep settings with the files and settings transfer wizard if you want, usually i like a fresh install.
I'm totally with MyCatt. Just about every upgrade I've done has lead to some sort of problem. Sometimes minor, sometimes major. I never give up a chance to do a freash install. It makes things run so much faster, and tends to get rid of lots of your old junk you forgot about...