MDAC cannot be re-installed, when a re-installation is attempted the message displayed is "MDAC has installed successfully" but the installation only takes a few seconds therefore not reflecting a true installation.
MDAC can be located and downloaded from the Microsoft website: www.microsoft.com
If MDAC is not installed correctly.
Do the following:
1. Go to directory c:\program files\common files\system\ado by typing in the path in the run dialog box (or via 'My computer').
2. Highlight all the dlls.
3. Then go Right ClickOpen. It will ask you what program to use to open and you select 'Microsoft Register Server'. If it does not appear click the browse button and select it from \winnt\system32. A message should appear for most of the files saying Registered Succeeded.
Some of the files will give this error and some will say successful. That is ok as some of the dlls don't need to be registered.
...Program Files\Common Files\System\ado\ms**.dll was loaded, but the DllRegisterServer entry point was not found.