VSTO Outlook Addin doesn't get loaded for non-admin user


Piyush Gupta


I am trying to deploy my VSTO Addin for Outlook 2003 for all users on
a machine by following these steps:

1. Change addin installer to add keys to HKLM instead of HKCU.
2. Build installation.
3. Install addin on target machine using user having Administrator
4. Run MS Outlook 2003 and verify that addin has been loaded properly.
5. Login as a normal user on target machine.
6. Run MS Outlook 2003.
7. Outlook tries to install few things before showing up the UI.
8. Addin doesn't get loaded. :(

There is following error in the event log:
The description for Event ID ( 0 ) in Source ( .NET Runtime ) cannot
be found. The local computer may not have the necessary registry
information or message DLL files to display messages from a remote
computer. The following information is part of the event: Unable to
open shim database version registry key - v2.0.50727.00000.

and few warnings like:
Detection of product '{90110409-6000-11D3-8CFE-0150048383C9}', feature
'ProductFiles', component '{66CD2C91-2A15-4DA4-BBD2-5EC1075F3C0E}'
failed. The resource 'HKEY_CLASSES_ROOT\.pip\' does not exist.
Detection of product '{90110409-6000-11D3-8CFE-0150048383C9}', feature
'WORDFiles' failed during request for component '{1EBDE4BC-9A51-4630-

But if I elevate normal user as admin and try logging again, addin
does get loaded. I think this must be pretty common requirement to
install addin for non-admin users on a target machine. Can you guys
suggest me any solution for this problem?

Appreciate your help,

Ken Slovak - [MVP - Outlook]

You do know that VSTO does not support registering in HKLM don't you? A VSTO
addin should be installed on a per user basis.

Dean Cleaver


I don't believe that is true, as I have mine loaded via Local Machine, and
it works fine.


Look into giving your strong name full trust - if you're unsure of how to do
that, I can send you a script later.


Ken Slovak - [MVP - Outlook]

According to Ryan Gregg of MS in the VSTO Web forum if an Outlook VSTO addin
is registered in HKLM then Outlook ignores it and does not load it.


Hi Ken,

Can you please tell me where this has been documented that the VSTO addins
are supposed to be installed per user basis ?

I also require a functionality that the installed VSTO addin to be available
for all users.

Ken Slovak - [MVP - Outlook]

It was in Ryan Gregg's blog I believe and he also mentioned it in some
answers he gave in the VSTO MSDN forum. I also was told the same thing in a
private briefing, but those public references should be enough. I don't have
URLs for that but I recall reading it a couple of times.

Ryan is on the Outlook team and works with Outlook programmability.

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