Windows XP SP 2
I’m downloading Windows XP Service Pack 2 even as we speak, as it hates viruses and worms and buffer exploits and other issues that have sort of become synonymous with the OS. I’ve had an earlier version on this machine as well as the laptop Gabe and I share - one of the more overt changes is to the control panels for using Wi-Fi, I think you’ll probably like that. Big Firewall changes, too. You can look at the release notes yourself while it downloads, but I found the review over at the Supersite for Windows to be more than adequate.