The program stopping KoDP from running can literally be anything. There are too many possibilities to know or list them all out.

To resolve your issue:
1. Start KoDP
2. One by one close non-OS processes
3. KoDP will appear once all offending processes are closed.

NOTE: More than one of your processes could be causing this problem. My wife had three difference processes that would stop KoDP from starting. It only took about 5 minutes of trying different process closing orders to figure them out.

There's an application called Game Booster that allow turning off processes you apply to a sort of black list one you turn on games (that is also on a list). That way you can run Game Booster with pre-configured processes that will conflict with the game then when you are done and turn off the game Game Booster will turn them back on. You can also add normal applications as well that you want to turn off.

I will try this process and see what happens.

The really frustrating thing to me is that I have owned KoDP since I joined GOG basically and it has worked without a hitch until just recently. I have the same computer (sadly), same OS, etc.

The only thing different is anything Windows Update has done and a few video card driver updates along the way.

Well, nothing works. I've shut down every process that doesn't seem to be essential and cannot get this game to run.

I do not understand what has broken this game for me.

This solved the problem for me!

Apparently, my wait chain involved a process known as rundll32.exe. I have no idea what that is or what it does but I as soon as I killed that process the game started right up just like it always has. Also, that process restarted itself as soon as I killed it but it was enough to let King of Dragon Pass get going.

Does anyone know what this rundll32 thing is?

I recommend anyone having this issue to analyze the wait chain and cancel any processes that Windows identifies.

rundll32 is an old method to execute code in a DLL directly from the command line (A DLL is a file that contains code which can be shared among programs). Microsoft has deprecated this method long ago because it has several disadvantages, not the least the one you've encountered: it makes it difficult for casual users to identify which program is causing problems.

If you want to find out who's calling rundll32 on your system, try the following:
1. Use the Analyze Wait Chain function to find the PID of the problematic process
2. In Task Manager, go to the Processes tab
3. Right click on the column headers, select Choose Columns, then tick "Command Line"
4. Find the process with the PID you got in step 1
5. You should now have a column which shows the exact command line that was used with rundll32, something like
"C:\windows\system32\rundll32.exe NameOfSomeDll.dll,SomeFunctionName"
6. Find NameOfSomeDll.dll on your system and you should what is causing the conflict with KoDP.

OK I grouched around until I figured out what works on the laptop this is on (1366 wide 15" dell laptop), after reading everything here.

Adding -w to the shortcut did NOT work - the window cut off the bottom of the game on my screen no matter what.
Didn't matter whether I checked the 640x480 or not. Adding <space>-w after the target did not help.

I was unwilling to make Windows fonts small, which helped some people with getting window mode to work, because I have older eyes and with glasses still need larger fonts.

Gave up on window mode as a lost cause and started over.

In the shortcut's properties, what worked was:
Selecting Win 98/ME compatibility mode
Ensuring <username> had full rights (they were not checked, even though <username> is also admin)
Keeping selected the other stuff GOG setup had already checked: Run in 640x480, disable visual themes, disable desktop composition, and disable display scaling on high DPI.

Now the game is running properly in fullscreen mode (it did not before, so the Win 98/ME compatibility must have been the only thing really needed to do the trick). So far, fullscreen 640x480 fills the 1366 screen without apparently cutting anything off, nor being too small, at least through the beginning of the game (where you make a bunch of choices to set up the game and then begin the game itself). Fingers crossed.

I can save with Alt-S, and quit with Alt-Q. So far I have begun the game successfully.

Also, some others have found that certain tasks under Windows seems to block the game's startup. I don't know about that, but this hasn't happened on my laptop. At least so far, KODP runs successfully, with plenty of other stuff running on this machine - I didn't kill anything - still have running browser, word, windows explorer, multiple security tasks, and lots of mlscellaneous stuff as well. (This laptop is a budget i3.) However I do have Windows "Aero" themes (which is on by default as wallpaper with a new Windows install) turned off. That is, I'm not using it for prettification. Oh, I have a changing desktop wallpapers, calling images out of any of a number of categorized folders of images I have created which are desktop wallpaper "themes", which change the picture every so many minutes. But these are not done under "Aero", just vanilla - because Aero runs scripts to do little visual transition effects that I don't need, because they interrupt my games. And that means Aero is not worth it. So make sure Aero is not in use if you are trying to rule out possible issues.

Thanks gog support discussion forum!

Thank you!

This worked on windows 10 for me, thank you very much. :D

The game gives mTRopolis windows player error "Failed to open document" and doesn't launch. No where in the internet is any mention of such message in relation to KoDP.

This is extremely frustrating.

Okay, there's a lot of good advice in this thread for anyone having issues getting KoDP to start, particularly using the Analyze Wait Chain function in Task Manager to identify conflicts.

I'm not going to rehash all of it, I just want to add two things:

1) On my Win 10 System, SKYPE was the culprit blocking KoDP from starting. I hadn't seen SKYPE mentioned anywhere else in the thread, and wanted to note it for anyone else coming along with the same problem.

2) On my system, KoDP starts and works fine with Google Chrome running in the background. YMMV, but I suspect that whatever conflict used to exist between Chrome and KoDP has been resolved.

That sounds like it may be a permissions error. Try this:

1. Right-click on the KoDP.exe executable (in your King of Dragon Pass directory)

2. Select the Compatibility tab

3. And make sure "Run this program as an administrator" is checked.