If you're really concerned about a virus, do the following:
(1) Download HiJack This available at:
http://www.spywareinfo.com/~merijn/
This software will list all programs that run when you start your computer.
(2) Do a System Scan, and look through the list. Any ones you are scared of at all, simply type the name into google.
For example, you see:
C:\Program Files\WinUpdate\winupdate.exe
Google winupdate.exe and BOOM! Tells you it's a trojan, and usually how to take care of it.
Or any you're concerned about, feel free to PM me your HiJackThis log and I can look through them.