I've not had to remove this one personally, but the methods are much the same.
You will need a couple of programs to help to start. Download these some of which are available on this site) or do a google search.
spybot search & Destroy
Boot into safe mode with networking (Press F8 on boot up).
run crap cleaner in each user profile
run adaware and spybot - make sure you update first
go to click here and do a full scan of local drives
Delete any found viruses/spyware
Do a search of the system for WinNB40.dll (make sure you search hidden files and folders). If found, either delete it or rename it to something like winnb40.old
reboot into normal windows.
If still there, you will need to run hijack this and do a scan only and paste the results here. Unless you know what to delete you could run into problems later.
Let us know how you get on.