Quick question. Anyone tried setting registry for gogwrap, so it sets cpu affinity automatically?

HKLM\Software\GOG.com\GOGHOMM3COMPLETE\AFFINITY=true
HKLM\Software\GOG.com\GOGHOMM3COMPLETE\AFFINITYCORE=1

or something like that. That way you shouldn't need any patch or tool.

Didn't have time to test it, but should work exactly the same. Unless gogwrap somehow protects its settings.

I'm sorry I'm trying to use this command line prompt stuff to do what you listed but I can't get anything to work. You're going to need to speak english on this one cus googling how to work it isn't helping me any.

ITT: Assume I'm dumb and don't know how to execute a command line prompt and walk me through it.

First, make sure you've placed the imagecfg.exe into your HOMM3 folder, where the Heroes3.exe is. Second, copy your Heroes3.exe and put the copy someplace else, in case something unexpected happens.

Open the start menu, and type "cmd" in the box at the bottom. It should bring up "cmd.exe" up at the top.
Right-click cmd.exe, and run it as an administrator.
Type cd\ and hit enter. (That's a backslash.)
Type cd followed by your HOMM3 installation path, in quotes, and hit enter. For example, { cd "Games\Heroes 3\" }
Type imagecfg -u Heroes3.exe and hit enter.
Type imagecfg -a 0x1 Heroes3.exe and hit enter.
Type exit and hit enter.

And you're done!

Instead of 'Open the start menu' you should simple press Win+R buttons on your keyboard (i.e. keep pressing Win button between Control and Alt keys and then press the 'R' button). Then release the buttons, type 'cmd' and press Enter. You should run it as administrator BTW.
"Type cd followed by your HOMM3 installation path, in quotes". Quotting isn't needed if you don't have spaces in the folder names. Typing
cd \Games\Heroes3\
and pressing Enter should be enough, for example (assuming your game is installed in \Games\Heroes3\). I don't recommend installing the games in default \Program Files\blablabla locations.
P.S. Thanks for this instruction anyway. :-)

The new Heroes 3 installer here on gog actually sets core affinity to one cpu automatically. So downloading the installer again here on gog should fix the issue.

I just checked. I have not altered anything about Heroes 3, only installed from the newest gog installer. Started the game, and opened up task managed, checked the Heroes 3 process affinity, it was using only one core.

Awesome, thank you for the walkthrough. Works perfectly.
Interesting, I'll have to check that out.

Is there anyone else that can confirm that this works?

Well even the new version crashes after an hour or two for me.

That is good to know. Thanks for sharing that helpful info. I know I'm coming along months later but would you or anyone reading this know if they patched the Heroes Chronicles games this way as well so I don't have to bother with it?

I did another check now on my windows 7 virtual machine. I have two cpu's allocated to running that virutal machine. Heroes 3 installed from the newest installer here on gog only use one cpu.
However, Heroes Chronicles make use of both cpu's. So gog have not fixed Chronicles.

You can make the change yourself using imagecfg as mentioned by bevinator, the desrciption provided in their post explains very well how to do it. Just make sure to change the paths to your chronicles folder. Also, each chronicles game has its own executable, located in a subfolder in the main chronicles folder. This means you have to change the affinity for each chronicles game to make them all use only one cpu.

Thanks for getting back to me. I downloaded a copy of imagecfg.exe and copied a very nice detailed set of instructions for running it against all the appropriate executables for the Chronicles games into a readme.txt then copied these both into my folder where I've got the installer for Chronicles. So I can take care of that when I get around to them.

I see this is a really old topic, but I still have the same problem. I launch the game using Gameranger to play multiplayer with my brother, but after some time the game crashes. I tried playing alone in single player and it seemed to work fine. At least long enough for me to lose the game.
The first time I played multiplayer however, it seemed to work fine. But I had to reinstall it because I realised I installed it on the wrong drive to start with. Since then, it keeps crashing around 10 mins into the multiplayer game (using Gameranger).
I tried the cmd method but it didn't seem to work for me. I get the following messages:
After typing: "imagecfg -u Heroes3.exe" I get a message:
Heroes3.exe contains the following configuration information:
Process Affinity Mask: 00000001
Heroes3.exe contains a Subsystem Version of 4.0
Image can only run in uni-processor mode on multi-processor systems
Heroes3.exe updated with the following configuration information:
Image can only run in uni-processor mode on multi-processor systems
Image can only run in uni-processor mode on multi-processor systems

And after tying: "imagecfg -a 0x1 Heroes3.exe" I get:
Heroes3.exe contains the following configuration information:
Process Affinity Mask: 00000001
Heroes3.exe contains a Subsystem Version of 4.0
Image can only run in uni-processor mode on multi-processor systems
Heroes3.exe updated with the following configuration information:
Image can only run in uni-processor mode on multi-processor systems
Image can only run in uni-processor mode on multi-processor systems

Is this supposed to happen?
Help?

You can safely ignore these messages. If no error occurs during this process then you're done right and can play HoMM 3 on single core.

Ok, I did this but it still freezes in mid game when I play multiplayer on Gameranger. The screen eventually freezes with the sound stuck in loops and a blocked cursor. Only thing left to do is [Ctrl]+[Alt]+[Del] --> Task Manager which says that it's not responding.
The thing that bothers me is that it worked the first time I played.
In the meantime, I uninstalled some other software but I don't see how this could have affected HoMaM3. Am I maybe missing some software/update?

PandoraInVein
Try turning off the music and sound effects in game options. See if this helps. If yes, turn on music/sound and try updating sound drivers. Then run dxdiag, go to Sound tab and try moving left (one position) the hardware acceleration slider.