not able to see addins in addin-manager, visual studio 2005

I want to use addins with my visual studio 2005. I have a couple of
addins on my machine, but I am not able to see anyone of them in the
addin-manager (tools->Add-in Manager).
I have already verified the .addin file of the addins and also made
sure that the path is correct.
Please let me know what am I doing wrong.