If you can’t enable or disable any add-ons in Internet Explorer then it is likely that there is a group policy that is preventing you from doing it. Like most group policies they can be temporarily overwritten by modifying the registry key. You can copy and paste the text in blue into a text file and give it the .reg exension. Now when you open it, it will modify the registry for you. Below the setting is set to 0 which means that you CAN enable or disable add-ons in Internet Explorer. Set it to 1 to prevent yourself from doing it. NOTE: HKLM is for all users, however if you go to the same path, but for HKCU the change will only affect you unless there is a value in HKLM which will then override the user value (I think).
Windows Registry Editor Version 5.00