Cannot disable add-in

I’m trying to disable some add-ins but I get the error;
“The connected state of Office Add-Ins registered in HKEY_LOCAL_MACHINE cannot be changed.”

How can I disable the add-in without uninstalling it?

Sounds like you are using Outlook on Windows Vista. However you can also get this error on previous versions on Windows when you are logged on as user and not as an administrator. To disable the add-in you must start Outlook with administrator privileges.

Windows Vista and Windows 7
Hold the SHIFT button and right click on the Outlook shortcut. From the menu choose "Run as administrator". Then press Continue or provide administrator credentials when prompted. Once you’ve made the change, restart Outlook to run it under the user context again.

Windows XP/2000
Logoff your user account and logon to the computer as an administrator. Once you’ve made the change, logon with your own user account again.

Note: See this Q&A for instructions on how to enable/disable add-ins.