When you want to deploy an Office Plugin programmed with Visual Studio Tools for Office then have a look at this Blog
One important thing which was not said on other articles is that on a 64-Bit OS the Registry Path for the Allusers is somewhere different…
4) Installing on 64-bit Operating Systems
Unlike the HKCU registry hive, the HKLM registry hive for Office add-ins is redirected on a 64-bit Windows OS. So if you are trying to register an add-in with 32-bit version of Office running on a 64-bit OS, the add-ins registry will be under the WOW6432Node. The 32-bit Office running on 64-bit OS will always load the add-ins listed under this key.
e.g. HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\application name\Addins\add-in ID
A 64-bit version of Office 2010 on 64-bit OS will always load the add-ins under this key:
e.g. HKEY_LOCAL_MACHINE\Software\Microsoft\Office\application name\Addins\add-in ID
With the ability to directly register and load VSTO add-ins from the HKLM hive on Office 2010, you can easily deploy VSTO add-ins to all users of a machine and no longer need to follow the steps outlined in Misha’s blog