Red X on the bottom right of my screen.?

I have windows xp and i was using my PC and suddenly it restarted and when it opened up again there was this red circle with a white X in it. It keeps on popping up saying my computer is infected and it says to click it to install the latest version of some antivirus. How do I remove it??????? Also I ran an online... show more I have windows xp and i was using my PC and suddenly it restarted and when it opened up again there was this red circle with a white X in it. It keeps on popping up saying my computer is infected and it says to click it to install the latest version of some antivirus. How do I remove it??????? Also I ran an online scan with geek squad and it said i have these.

C:\WINDOWS\karna.dat is infected with Trojan.Perfcoo
C:\WINDOWS\system32\karna.dat is infected with Trojan.Perfcoo
C:\WINDOWS\system32\drivers\beep.sys is infected with Hacktool.Rootkit
C:\WINDOWS\system32\dllcache\beep.sys is infected with Hacktool.Rootkit

PLZ HELP. THANK YOU
3 answers 3