MDAC20_a.cab is no longer available.  Please use MDAC_TYP.EXE instead.  
This file can be found in the MDAC 2.0 SDK and on the Visual Studio 98 CD.

MDAC_TYP.CAB is provided for the use of the VB Setup Wizard.
MDAC_TYP.CAB is not intended to work from the codebase tag in an HTML page.	
Users needing the functionality of MDAC 2.0 on their workstation should run the MDAC_TYP.EXE file to install those components.