xp pro, click on icon and freeze

I have XP Pro, SP2. When I click on an desktop icon the system will freeze. When I try to explore it will freeze. I have to use task manager to open up programs. I suspect a virus, does this sound like any symptoms of any particular ones..
Did an online virus scan and came up with nothing.
This machine has cable internet with no virus protection.. real nice…any help for my friend..