To my surprise the DOS software for proLIGHT mills will run under XP and it can communicate with the machines. I can hit F4 and manually jog the mill. The problem is no matter how I've tried setting the compatibility and memory settings using a shortcut, after I load an NC file and hit F6 to run, it crashes with a "Conventional Memory Exhausted" error despite showing plenty of free space.
That's odd because I've been running my mill from an old laptop booted off an unmodified DOS startup floppy made with Windows 7, no drivers for extended or expanded memory, just the 640K that a bare bones DOS environment has. The manual states that Quarterdeck QEMM works better with the PLM2000 program than the manager that comes with MS-DOS.