|Sorry, lemme restate that. There are a lot of processes that need to have full control in the background usually. I can't say if you are being hacked or not. Since you have had a problem then your system has not been set up well enough to be sure.|
Now, if you suspect you have a problem and you feel that it is worth fixing then you ought to fix it.
What I would do is get the updates like SP2 on a CD. I would get current antivirus and a good firewall program on CD. Have those programs tested for virus's. Disable internet. Then I'd do a clean install, update, install firewall, install A/V. Then I'd make a limited user to use for 99% of the time. Use an Admin account only for installing software or other tasks that must have admin rights.