'80040154 Class not registered' with interop from ASP.NET

Question

I\'m receiving the following error on a Windows XP Pro SP2 x64 machine running IIS6:

System.Runtime.InteropServices.COMException: 
Retrieving the COM class f         


        

Answer 1

Make sure that your application pool is either 32 bit (or supports 32 bit apps) or your COM control supports 64 bit apps. Most likely, your native COM library is 32bit and your pool runs a 64 bit worker by default, which is unable to load 32bit COM dll.