What operating system are you using? How much memory (RAM) do you have in your computer? How many progams do you have starting at bootup? How many program icons are present in the lower right hand corner of the Task Bar?
If you truly believe it is a virus, and you are using WinXP or Win2000, then you could try scanning with Ewido.
You can download a trial version of Ewido here: http://www.ewido.net/en/
Be sure you update it before using it, and when it finds a problem, be sure to select the check box to do the same action (clean) when it finds a problem, otherwise, you will have to click continue, to keep scanning with every problem it finds.