ERROR: CDOEXM failing with code 800A0030

I have seen this problem many times where people complain me that they are recieving the following error

Error: Error in loading DLL: 'oExch.DataSource.Open', Code 800A0030

DataSource.Open command returns instance of CDO.IDataSource interface which is part of CDOEX.dll
Possible cause could be CDOEX.dll not registered properly

Re-register CDOEX.DLL which should resolve the problem