If you’ve installed an add-in to Outlook 2007 that you now suspect to be causing Outlook to misbehave, you can disable it quite simply using the Trust Center. However, if you’re also using Windows Vista, or some another OS, you may encounter a curious error message telling you “The connected state of Office Add-Ins registered in HKEY_LOCAL_MACHINE cannot be changed.”
Thankfully the workaround is simple. To disable your bogus add-in you must start Outlook with administrator privileges:
Windows 7
CTRL+SHIFT click on the Outlook icon on your taskbar to instantly launch the program with administrator privileges. Or create a new instance of the Outlook program icon on your desktop, then right click on it and select Properties. Under the compatibility tab set the Privilege Level to ‘Run this program as an administrator’. Once Outlook opens in administrator mode, disable the add-in in the Trust Center.
Windows Vista
Right click on the Outlook shortcut and choose “Run as administrator”. Once you’ve disabled the add-in, restart Outlook to run it under the standard user credentials once again.
Windows XP/2000
Log off your user account and log back in to the computer as an administrator. After disabling the dodgy add-in, logon once again with your normal user account.