I apologize if this has been asked before, but how do I change the size of the screen.

I try to play Might and Magic, and the game window fills the whole screen. Using the Windows key makes it too small, and I can't undo it. Does anyone know how to make it slightly smaller?

Which game exactly Might and Magic 1?

If it's one of the DOSBox games (1-5), you can press Alt+Enter to switch between windowed and full screen. I assume it's one of those, since pressing the Windows key does it too (but you have to press Alt+Enter to return to full screen).

If the windowed version is too small, you can increase its size by editing the Dosbox configuration file. Go to the game folder where you installed it and find a file called dosbox.conf or similar (probably dosboxMM.conf). Edit it in notepad. Find the line that says windowresolution=original and change it to what you want. e.g.

windowresolution=800x600

Note that these games were meant for 4:3 ratio monitors.

Thank you.

Alternative solution:
edit dosboxmm1.conf and modify two lines into the following:

fullscreen=false


scaler=normal3x