From the Shiny MDK Patches page:

When upgrading, here is the way to work out which MDK CD version you have. When you first installed the game from the CD, flags […]
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When upgrading, here is the way to work out which MDK CD version you have. When you first installed the game from the CD, flags appeared on screen....

USA VERSION = 3 Flags
EUROPEAN VERSION = 6 Flags
GERMAN VERSION = 2 Flags
Patches are the same for the European and USA versions.

Final Patches:
Each file is a zip file, with an executable and a readme file.

From the Shiny MDK FAQ:

Q. When I downloaded a patch, I got a message that says it's "Incompatible" with my version of MDK. What does that mean?
A. There were two different executables, the censored and normal versions of the game. Thus, we have two different patches that do the same things. If the patch you downloaded doesn't work with your game, it's probably because you should have downloaded the other version. Getting the other version should fix the problem.
Note: The patches will not work with the demo version of MDK, or any version that came with a piece of hardware (i.e. ForceFeedback joystick, a video card, etc.)

Patch still available here:
http://www.falconfly.de/patches-mdk.htm

Wow, sorry I missed that info. Thanks akula65, I'll try it when I get home and post back.

BTW, love Wallace & Gromit.

Thank you - one step closer!

Updated my DirectX to 9.0c. Tried the US patch version but kept getting the "MDK Executable Version Is Incompatible with MDK CD" error with MDK3DFF.exe. My version is US (3 flags during install). Decided to give the German patch a shot and sure enough, MDK95FF.exe works great!

Just curious - does anyone have a German copy of MDK3DFF.exe or know how I can get the Direct3D version running with FF?

Very close - thanks for the help thus far!

Resurrecting this long-forgotten thread since the OP and I have the same goal in mind: running MDK on Windows 98 SE with the Microsoft Force Feedback Pro.

I have the aforementioned joystick, a retail MDK CD, and a W98SE PC with a gameport provided via an Audigy 2 ZS. I found the FF patch that matches my CD, but when I start the game, I see - in the MDK gold text - InitForceFeedback Failed with a hex error code. Google literally reveals nothing about this error. Has anyone else seen it before?

Force Feedback works in the Sidewinder Control Panel, and in another game that I've tested (Rollcage).

Edit: Since I was rude enough to necro this thread, I might as well post what fixed my issue.

The required file mdk_ff.dll is in some of the mdff_*.zip archives, but it's considered a "system" file, so it doesn't show in Windows with the default viewing options. If you just drag-and-drop the archive/folder contents into the MDK directory, you will miss it. Either use the unzip tool to specify a destination directory, or make sure you're viewing all files in Windows before you copy the patches.

It was worth the effort. The feedback effects in this game are extremely well done.

Leaving this here if anyone ever try to run it on winXP.
I've got mdk ff to work on on a winxp machine... BUT... The game does not detect any axis movement.
It does send force feedback commands to the device and it does detect the buttons. It just does not have any analog movement. Super weird.
I don't have a machine with win98 so I can't really test it. But looks like it does not work correctly under XP.
BTW, the normal non-ff version of the game works correctly with the joystick including analog movement. I believe that the game requires the Sidewinder software to be installed. And it can't be installed on winXP.