|I just went from IE7 to IE8 on my XP clunker. There is a stand-alone file you can download to install IE8:|
Knowing MS I thought that was the installer file but it's not. It's only 16 meg but it expands and does a complete installation. However, I think you'll need at least SP2 in order to install it. At one time you could order SP2, SP3 and IE7 on cd from MS. I don't know if you still can but that's how I installed them on my computer. If it's possible to still order them then that's what you should do. You might take a look on ebay too and see if anyone is selling them. If you absolutely can't find those disks I suppose I can burn you copies and mail them.
Once you get IE8 installed there's a recommended cummulative security update--
IE8-WindowsXP-KB2618444-x86-ENU.exe--you should install. If it doesn't show on the IE8 download page you can google the file name and find the download site.