i dont suggest hijackthis to novice users.
edit
uninstall NIS
Reboot in safe mode
run your task manager
goto the process tab
and look at the process that are running
get the name of each file…
such as taskbar.ext or so forth
goto this site here
http://www.processlibrary.com/
search each process and see what comes up
that sould take care of most stupid viri/trojans
some nasty ones will infect system files and just become a part of the system file
also look at ur regedit and see if you notice anything wrong in the startup folder.