Heroes 3 issues under XP or Vista.

set compatibility with Windows 98. (right-click on the shortcut => compatibility => Windows 98)

Thanks for the advice!
Only one "Shadow of Death" started working, and I have a licensed copy, but the disc is lost. And it won't run without the disc.

All the others still refuse to work, darn it! :(
I've already tried providing them with different files - it's useless.