Update keeps screwing up my system

I have XP home edition and Everytime I go to update my computer either using the automatic update or going thru Microsoft, my display is completely scrambled and I cant use my computer. I think Its service pack 1 that I cant install. THe only way I seem to be able to fix it is to restart in Safe mode and and use system restore but now I'm unprotected. How can I get my PC to work???