Two weeks ago installed windows xp-pro on a laptop with all security updates etc. Java (the latest), Foxit (the latest), IE8 etc. to keep it short. I setup a user account, added it to a domain, set the user as "Power user" (no admin rights).
Pufff, done in less than two weeks. Pop-ups slow as sin.
Words of advice, install an AV it might not work well and give you a false sense of security, but might last a bit longer between re-preps.
I never tried the Microsoft AV, but from what I read. it's free.