PC boots in a loop

Yesterday AVG detected a virus in a system file which i deleted without really meaning to and now my PC boots up until the windows load screen and then reverts back to the start. I've tried booking from the XP CD but the same thing happens.

Im assuming that i need to restore my system back to a date that it worked but im not to sure how to go about it. Any ideas?

 

Have you tried booting to Safe Mode? If you can get there, you can run System Restore from there.

What was the name of the infected file you deleted? Is it deleted or merely quarrentined?

 

Safe mode is F8 isn't it? im just getting a clicking noise whenever i hold it down at start up.

 

Yes, pressing F8 at as the first boot screen fades will invoke the Advanced Options Menu and you can select Safe Mode from there. Do not hold the F8 key down, rather repeatedly press it rapidly as soon as the first boot screen fades.