You have to create the DOS P/M disks from a working copy of P/M. It is a normal part of the install routine. Suggest doing that on another machine, then use those disks on your system. It is a bootable diskette that P/M makes.
But, PowerQuest is hard at work on a patch to make P/M 5 work in ME. They are aware of the problem. It centers around the immovable files created by ME as part of the SYSTEM RESTORE function.