Windows XP SP2
So you know the second service pack for WinXP is out. Well, if you've got and always-on internet connection and the Auto-Update thing going (and if you're not sure, you probably do) then you probably have it by now. If so, go to the next message; there's nothing for you here.
An upgrade this size will break things. End of story.
Me, I'm going to wait a while. I got firewalls and pop-up blockers and enough sense about what to run and what to open that I haven't had a virus in years and don't run anti-virus software after the free subscription on a new machine runs out.
If you're so inclined, you can check out what SP2 has in mind for you. If you've got all new software, if you use nothing but Office, IE and Outlook you'll probably have few issues. Me, I'll be eavesdropping on all the newsgroups related to my development tools and I'll need to see a general acknowledgement that stuff works before I apply it.