There you go. Much as I find the jump to Vista or 7 worth it from a UX perspective, that combination should keep you OK for a lot of things (and when one or both of those drop XP support, you've potentially got Firefox, or Opera, plus a comparable software firewall -- which I haven't followed as I no longer support anyone using XP, but there at least used to be alternatives and I'd be surprised if there weren't.)

For many people, Flash quitting XP support may be an issue as well, although I'd imagine in your case you're going to just disable it, if you've got it installed at all.

Linux + Wine or CrossOver is probably your next step on older hardware once XP goes a couple steps further to the unsupported.