Check for the sasser virus. Check MS website, they have detector/remover tool, as do most AV sites.
Check registry keys in the run box like these
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
CurrentVersion\Run "avserve3.exe" = C:\WINDOWS\avserve3.exe
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
CurrentVersion\Run "avserve.exe" = C:\WINDOWS\avserve.exe
You could also try to find and delete/rename these files. Search the whole HDD.
Make sure to check C:\_Restore folder.
To remove this virus "by hand", follow these steps:
Here is what McAfee had to say(for one of the variants) :
Reboot the system into Safe Mode (hit the F8 key as soon as the Starting Windows text is displayed, choose Safe Mode.
Delete the file AVSERVE.EXE from your WINDOWS directory (typically c:\windows or c:\winnt)
Edit the registry
Delete the "avserve" value from
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Reboot the system into Default Mode
Good Luck
to perform registry edits, you need to run regedit from start/run box. Standard reference to changing registry keys here. (Please be careful.)