also, it could be that you are being slowed down by 'legitimate' but unnecessary processes. the most common things i see on XP machines that eat up lots of resources are: HP printer crapware and Windows Desktop Search.
uninstall WDS if you can. you can still do searches without it.
hp printer crap is too complicated for me to discuss, except that i try not to install hp printers with 'the cd' that comes with them. i try to install them by downloading 'basic' drivers from the web.
you could play around with 'msconfig' as well to try to determine what is bogging things down. i wouldn't mess with the services tab, just the startup tab. if you don't recognize the manufacturer or it seems otherwise suspicious, disable it, reboot, and test the waters.
Bret, if you really want a reliable machine with no viruses, I suggest booting a Live CD of whatever flavor of Linux you prefer. As long as a web browser is the primary application you will need, you should be good to go. LinuxMint is nice and clean and comes with Firefox pre-installed. Or a Chromebook would work well. You do have choices! Actually, even an iPad with a bluetooth keyboard may fit your needs.
i could never seriously recommend linux to someone that doesn't consider themselves a 'computer person'. it is an austere lifestyle. it is a bit like living 'off the grid'. i like it (both linux and 'off grid living'). i consider them to be ideal ways of living.
Twinkle...Mr. Spock? Is it...really...a crime...for a captain...to have a little twinkle...in his eye? lol
i've always thought it delightful that William Shatner is considered to be overly dramatic and his name is so similar to William Shakespeare...and that Star Trek is so fond of using quotes from Shakespeare.