Removing the right click item is the easy part - it is a simple edit of your registry. See
http://www.personal-computer-tutor.com/vic11.htm
for a description. BACK UP YOUR REGISTRY FIRST.
The more worrying thing is what else has been done to your system. I would imagine that someone used an active-x or java routine to install the right click. Could easily have installed something more nasty too.
Here are the obvious questions: Do you have an antivirus application with the latest virus definitions? Is it active? When was the last time you scanned? Do you use a personal firewall e.g. Zonealarm? Have you checked that its not been compromised? If you use Internet Explore, Outlook Express or Outlook, have you installed the latest security updates (go to windows update)? Answer no to any of those and I'd suggest you remedy this.
Next is to stop any future opportunity to manipulate your system. Change your security settings to deny unsigned active-x and ask permission before downloading ANYTHING. Same with Java applets. If you use Outlook or OE turn off the preview pane.
Hope this helps.