Specifically, I'd like to free up HMA like one would do by removing the "HIGH" from "DOS=HIGH,UMB" in MS-DOS 6 config.sys files, but I'd also like to manage other types of memory if possible. Can this be done? I have a program that has to be run using a DOS boot disk, and running it within Windows in compatibility mode or with other versions of DOS aren't options. With a vanilla XP DOS startup disk the program is unable to read 100000h, so I'm guessing the problem is with HMA right now.