QUOTE (Michael W @ Aug 26 2008, 16:35)

I'm the only administartor, there only is one account (mine) on the laptop. Virus scans have revealed nothing,so I'm not sure whats causing it.
What OS are you using? As you will have an administrator account, even if you only see your named account when logging on. For example, look at the difference between going to the User Accounts dialog in the Control Panel to the actual user accounts accessed through the Computer Management dialog.

Spot how the User Accounts only shows my named account (the one I used at the very end of the OS setup) and the guest account (disabled) while there are several more security accounts. It is the permissions of these that allow you to run applications (inc. the task manager) on your PC.
I log into the PC with my Ric account, which itself is in the group "administrators". If you right click the name of your login account on the right hand panel in the Computer Management dialog you will get another dialog shown, click the Members Of tab of that dialog and you should see something like..