Excel Add-In deployment problem

I built an Excel add-in with VSTO 2005 SE, which I deployed to a user base that is predominantly Office 2003-based, but also with several workstations that have Office 2007 installed on them.

On the Office 2003-based workstations, the add-in works perfectly.

Now because this add-in was created with the version of VSTO for Office 2003, the add-in does not have a ribbon, and should show up under the add-ins tab when Excel 2007 is opened.

However, on the Office 2007-based machines, the add-in fails to show up. When I check the registry under the [HKLM\Microsoft\Office\Excel\AddIns] key, the LoadBehavior is set to 0, which I believe indicates that the AddInLoader.dll failed to even start (got deactivated). Strangely, when I changed all the keys to HKCU and not 开发者_开发百科HKLM, the add-in magically started to show up and work.

Does anyone know if the Excel 2007 has a restriction on the registry keys to HKCU only? If someone can help bring some insight, I'd really appreciate it!

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From here:

By default, applications in the 2007 Microsoft Office system can only load add-ins that are registered under HKEY_CURRENT_USER. To load add-ins that are registered under HKEY_LOCAL_MACHINE, computers that have these applications installed must also have hotfix package 976477 installed. For more information, see http://go.microsoft.com/fwlink/?LinkId=184923.