[Computer Dummy]

Hey I've seen a few posts similar to my problem but none of which I think were too relevant for my Win XP.
Basically I was infected by a trojan a while back. I managed to remove one of them, but im pretty sure there was one still there as some symptoms remained.

My cpu usage was between 95-100% after i had the trojan. This meant my pc kept crashing and i had to reset it constantly. The trojan didnt allow me to system restore and I tried just about every spyware and anti-virus programs available but it was still unusable. When I "ctrl + alt +del" SVCHOST.EXE seemed to be running more programs than usual. If i tried to stop the process of certain svchosts then it would tell me my comp was 'closing down in 100 secs, 99 secs 98secs etc'.

Now I cannot startup my pc without it freezing either in the login screen or the 'windows is starting up' screen. It also wont let me use safe mode.

Is it the virus, a hardware fault or maybe a combination?

Any help would be appreciated,
Cheers