Can't log into windows (no safe mode)

i have had a few viruses torjans for a while and so i downloaded all these anti virus and removed all but a few. So i got Panda Titanium when i installed it, it froze.
when i start up my computer it loads my personal settings and loads only my desktop picture and i cant do anything, few minutes later it automaticly restarts and goes to Log in and so i Click my account and i enter and same thing i see my desktop picture and a few minutes it restarts and goes to the windows xp log in again, it just keeps doing that.

ive tried going to safe mode but it wont seem to let me ive tried all of the F keys and Delete key..

now i am on my old old computer

 

Tape the F8 key every second. You are infected and maybe your best bet is to re-install.

Mount the HD in the old pc to copy datd, after scanning and then rebuild

 

what OS are you running?

 

I am running XP home