Haven't tried this yet but saw this on Microsoft's site:
"Special Considerations for MDAC 2.6 and Later
MDAC 2.6 uses a new mechanism for uninstalling. During
MDAC 2.6 installation, any previous version of MDAC is noted and copied to a backup directory. You can use the DaSetup.exe utility with the /u switch to roll back to the previous version of MDAC that was installed on the computer. Again, in MDAC 2.6 and later, you cannot use Component Checker to reconfigure MDAC; you should use the DaSetup utility instead"