slow running PC

[Roland Deschain]

I am in the process of looking at a friend's PC which is running slow. In Windows Task Manager there is a process running (synchost.exe) that is using 99% of the cpu. When I end the process the PC runs fine but when I re-start  it runs again.
There are no programs running and in the applications tab, nothing is shown.
How can I find out what is using it and stop it permanently?
The OS is XP home

[Roland Deschain]

I have found out that it is something to do with AVG free. If the system tray is disabled in startup the problem goes away.
Is this safe?

[SHAAN]

No, that would not be the problem may be possible that your antivirus files may be infected. Try any good boot time scanner and scan the whole system and install some good antispyware program. That will solve your problem.

[tdee]

  I would go here
http://www.bleepingcomputer.com/forums/topic182397.html
These people are well trained in removing viruses and spyware and I am betting that is your problem.
tdee