http://answers.microsoft.com/en-us/windows/forum/windows_other-gaming/heroes-of-might-and-magic-v-will-not-run/f356b2c9-6063-49ee-9a2a-4934e606d927

I actually bought the collection which included I, II, III, IV and V with 
all expansions.

Initially i couldn't install any of the games (windows versions not DOS) 
which was a pain (running win 7 64 bit), but after hours of Googling the 
issue. I found a gem piece of advice.

    Run Windows in Safe Mode
    Install game
    Revert to Normal Mode
    Play Game
    YEHHHHH WIN 7 64 bit running HOMM I, II, III, IV with no issues.

Hope this may help some one, somewhere down the track.