Problem

The Microsoft JET 4.0 Driver, which can open .MDB / Access Files, is only available for 32-Bit Systems

Ansatz – Approach

Register the DLLs for the operating system

Lösung – Solution

Solution 1 (Especially for IIS)

In IIS 7.x click on the app pool of your application -> advanced settings and look at the „General“ Section. The second Attribute is „Run in 32 Bit mode“. Check this.
Restart IIS.
If it is still not working, go on with Solution 2.

Im IIS Manager markiert man den AppPool der Anwendung und kann rechts auf „Advanced Settings“ (Erweiterte Einstellungen) klicken. Im „General“-Abschnitt (Allgemein) kann man im 2. Attribut sagen, man möchte im 32-Bit-Modus starten. Danach sollte der JET Treiber auch gehen.

Solution 2 (Especially for local applications)

The solution is to manually register those DLLs.

go to Start->Run and type cmd
this starts the Command Prompt
(also available from Start->Programs->Accessories->Command Prompt)

type cd .. and press return
type cd .. and press return again (keep doing this until the prompt shows :\> )

now you need to go to a special folder which might be c:\windows\system32 or it might be c:\winnt\system32 or it might be c:\windows\sysWOW64
try typing each of these eg
cd c:\windows\sysWOW64
(if it says The system cannot find the path specified, try the next one)
cd c:\windows\system32
cd c:\winnt\system32
when one of those doesn’t cause an error, stop, you’ve found the correct folder.

now you need to register the OLE DB 4.0 DLLs by typing these commands and pressing return after each

regsvr32 Msjetoledb40.dll
regsvr32 Msjet40.dll
regsvr32 Mswstr10.dll
regsvr32 Msjter40.dll
regsvr32 Msjint40.dll