SP2 Murdered my XP Home - continuous reboot

I installed SP2 so it would stop showing up in my taskbar. Once I did, the
computer gets to the XP screen with the scrolling bars and immediately
reboots. I tried a Windows repair to no avail. I upgraded to XP Pro, no
change. I found I can run msconfig and boot up with basevideo checked and it
boots OK, but the res is 640 x 480. From there I can adjust to 1280 x 1024
and it works just fine until I reboot. Then I go through the same thing all
over again. I am running a nvidia FX 5200 display adapter and updated the
driver to the most current version, no difference. I tried replacing the
kernel32.dll file, made it much worse. I need a genius!!!