TOK
You probably need to log on as 'Administrator' rather than 'User'.
More
HERE
where it tells you:
Disabling all access to add-on management
To turn off the Disable option and the Enable option for all add-ons, follow these steps:
1. Click Start, click Run, type regedit, and then click OK.
2. Locate the following registry subkey:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Internet Explorer\Restrictions
Note This registry subkey is available only in a domain environment where access to add-on management is disabled through a group policy by an administrator.
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type NoExtensionManagement.
5. Double-click NoExtensionManagement, and then type 1.
The following are the values that you can specify:
0 - The user can enable or disable the add-ons.
1 - The user cannot change the status of any add-ons.
6. Click OK, and then quit Registry Editor.
To set this registry entry as part of Group Policy, follow these steps:
1. In the Group Policy Object Editor, expand Computer Configuration or User Configuration.
2. Expand Administrative Templates, expand Windows Components, expand Internet Explorer, and then double-click the following policy setting:
Do not allow users to enable or disable add-ons