re-installing windows is not too much hassle. What is is often the sheer volume of downloads to do from windows update to get to service pack 2 then to download that and to install that and the updates afterwards. I would just go for the installation though give yourself about 4 hours to do this however. Also if you happen to have one of the rare but out there XPSP2 discs then installing that immediately after windows is also advisable if not then set up your net connection and go for it with windows update.