Very Strange - Class Not Registered Error

From: RichardF (RichardF_at_discussions.microsoft.com)
Date: 02/18/05 

Date: Fri, 18 Feb 2005 04:19:03 -0800

Hi,

I had this problem on a clients site the yesterday and I wondered if anyone
was able to shed some light on it.

(Win2k, service pack 4). (Win2k comes with MDAC2.5 preinstalled)

The application was producing "Class Not Registered" error message on
Connection.Open ("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Db.mdb").

For a testbed I creating a .udl file, with the same Provider and path to the
database and then Pressed "Test Connection" buttton. This produced:

Test Connection failed because of an error in initializing provider. Class
not registered.

if i pressed it again i get:
Test Connection failed because of an error in initializing provider.
Catastrophic Failure.

So I tried all of the following:
Installed Jet Service Pack 8 for win2k
Installed MDAC 2.61
Rollback of MDAC 2.61
Installed MDAC 2.8
Installed Visual Studio 6
Installed Office 2000 Pro

None of these helped and the orignal test always produced the above errors.

I also Installed Microsoft ADO Component Checker and everything seemed ok
(although some files had different versions).

A search on the internet revealed :
http://support.microsoft.com/kb/q275917/ - downloaded dsclient but this
was for NT.
Other hits mainly suggested reinstalling MDAC or Jet Service Pack.

I was at a complete loss and had run out of things to do. (It would have
also been helpful to know which class was not registered.)

Can anyone suggest reasons as to why this occured or how i can fix it.

Thanks in advance,
Rich.