I can honestly say in the four years I've been using XP i've never had to reinstall once, I can only remember having one blue screen in all that time (which was my own fault), i've not had a single virus or even serious spyware problems.  I think if you keep windows up to date, and your careful about what sites you visit, run a firewall, anti-virus and anti-spyware software, keep the registry clean, and don't run as admin (even though I and most other people do) their shouldn't be to many problems.  I've actually had a lot more kernal panics with linux than BSODs with windows, even though I use win XP 95% of the time.