The first thing to do in order to "harden" your windows (yeah yeah, I can hear all the Linux-guys laughing) after re-installing is to disable all non-necessary services.
Try this great little tool, it explains what the service does,why it might be a risk and what problems disabling it might produce :Security & Privacy Complete
Security & Privacy Complete is mainly a security tool for Windows.
It can disable all services which might be a security-risk, harden registry settings...
Also included privacy features for Internet Explorer, Media Player, and of course: Mozilla Firefox.http://sourceforge.net/projects/cmia/
btw : NEVER re-install windows without removing your net-cable first, DO NOT connect to the internets before you have installed a decent firewall and ...
DO NOT surf the internet from the admin-account (unless you trust the site(s) 100% ..
..and that's still risky) .
Be careful with installing ANYTHING unknown, especially if some website tells you that
"you must install (enter name of un-needed crap-ware) in order to view our images" or whatever ..
If you install anything then get it from the programs official-website and READ THE SMALL PRINT ..
Lots of "free" non-GPL programs install "toolbars" and other cash-generating crap-ware ..