I am dealing with word automation and when i am running my web application in XP OS it is quite fine running. Then I deployed this site into server (OS is Windows 2000 advanced server) where I met with problem. So I installed VS 2005 in this server and I debugged where I got this error.. Unable to cast COM object of type 'Word.ApplicationClass' to interface type 'Word._Application'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{00020970-0000-0000-C000-000000000046}' failed due to the following error: Library not registered. (Exception from HRESULT: 0x8002801D (TYPE_E_LIBNOTREGISTERED)). If anyone helps to solve my problem that would be appreciable as I have been struggling with this problem for last week. I have office 2000 premium in my server machine as well.