I had the EXACT same problem.( getting error about file missing when trying to double click the icon to start the game ) this is how I FINALLY fixed it...
right click the might and magic icon on your desktop and select "properties".
next press the buttons "find target"
you should see icons. double click the icon that reads mm6_12xp ( I think this was a patch that I downloaded but I don't know ).
then you should see a message that says "insert disc 2"
insert the disc and the game should automatically start.
This will work.
Best of luck and enjoy the game!!!!!