What is VMM32.VXD and what could be wrong with it?

Trying to install Windows Me, from original CD - it has worked before, no problems, and please don't ask me why I want to mess around with Me still - but every time, after it goes through the initial CD setup process, it hangs on the intro screen when it's supposed to boot from the hard disk.

If I leave it for ten minutes or more, it spits an error message about how VMM32.VXD is not found or damaged.

I can't get past that.

I'm just wondering what does that mean? What should I do?

Thanks.