Hi,
Try using F4 while the game is running. I think that will change the display to windowed mode. You may need to set your desktop display properties to 16 bit though.

Is there a way to force windowed mode, without changing the color depth though?

I didn't find one...

The above post is the answer. Just remember to hit F4 mid game to switch to windowed mode. Looks a lot better too since it isn't stretched!

Thanks, this did the trick for me too!

I've installed the 32bit patch and have used f4 to enter windowed mode as suggested, but now the game freezes so frequently as to be unplayable. I run windows 7, and have tried it both in windows xp sp3 compatibility mode, and without compatibility mode at all.
Any suggestions? Has anyone gotten this setup to work in windows 7?

Thanks a lot, mate! That patch made my day since I love to have my HoMM III window opened somewhere, but hitting alt+tab everytime I wanted to make a movement or check my e-mail was highly annoying. Now it's no more because of the brand-new Vista-compatible windowed mode :)

Search your registry for HoMM3 entries and look for this key:

"Main Game Full Screen

Change the value to 00000000 and save. That's it.

This thread is really old, but for anyone else wanting 32bit windowed mode, just use the HD patch: http://sites.google.com/site/heroes3hd/

It also allows you to change the resolution, and adds other awesome things.

Thanks Mephe, working like a charm.

I have a 64bit amd processor (new computer) and want to load heroes three (also am using windows 10).

YOU'RE A GOD !!!

Thank you! This works brilliantly. The other (old) solution caused performance issues, but this runs smoothly and is way more customisable.