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I had a quick search around for this, and it seems to be controlled by a Windows Registry entry:
The value should be zero, and then you should get your IE options back.
Before doing that, however, you might want to search for the underlying cause - and spyware or a virus in a pretty likely culprit. Try Spybot Search and Destroy and a full virus update and scan and see what comes up.
After you've done that you can usually edit the registery by clicking on your START button, select RUN and type REGEDIT. This will bring up the registry editor. You can then go find the Key that Encyclo pointed out and make any change that is necessary.
Be VERY, VERY careful when you're in the registry editor. A mis-click on something or an incorrect change in the registry can cause a lot of problems with the system overall.