Are you editing the VM settings after you edit the XML file? If so that will clear any edits you made to the XML directly. I had to install a floppy to my WFW3.11 VM in order to install DOS 6.22 and WFW3.11. To do that I edited the XML file directly. It was persistent so not sure what your problem is if you are not editing the VM settings after you edit the XML - sorry.