On a PC, Ctrl-Esc opens the start menu, although it won't give you the other shortcuts. (Lenovo used to have an app that remapped right Alt to the Windows key, for the ThinkPads, but...)
On a Mac, you've gotta remap it, it's in System Preferences, Keyboard & Mouse, Modifier Keys. Usually, how I remap a Model M is to move Ctrl to Caps Lock, Option to Ctrl, and Command to Option. So, for Option, you'll press Ctrl, and for Command, you'll press Alt.