I am trying to install my Outlook Addin on client computers.
Unfortuantely, the Add-in can never be \'Enabled\' it is always shown in the Disabled add-in section.
I think this tutorial might be useful for your reference.
http://msdn.microsoft.com/en-us/library/ff937654.aspx
Also, there are a few other things that you might want to check out. First, see if you have any COM exceptions thrown when you start up Outlook Addin. Normally addin will not be disabled automatically if it throws errors on startup. And you also want to have a look at loadBehavior registry key and see what values you got in there.
For details of LoadBehavior reg key, please refer to: http://msdn.microsoft.com/en-us/library/bb386106(VS.100).aspx