Is there anyway I can tottally restore my computer to factory settings?

Ok, so my computer has randomly been restarting on me. So, I ran a virus scan and got rid of a few and what not. Then the next day I turned it on and everything looks different. Even though it's XP it will only show clasic settings and there is no audio device installed anymore. I can't do a System Restore cause all the sudden all my restore points are gone and I can't use AIM of Firefox anymore. Does anyone know what happened and how to fix it? Or can I just start fresh. Oh and it says its in safe mode once in a wile and I can't find where I would have turned that on! I'm not computer illiterate I have tried msconfig and anything I could think of. Help please!