The notion that Windows XP cannot run DOS apps for some technical reason is poppycock. They just did a lousy job with the DOS support.
I am running VMWARE in WIndows 2000 Professional, and have Windows XP running as a virtual machine, and Windows 98, Windows ME etc.
The ONLY one that produces the 100% CPU usage when running some DOS apps is Windows XP.
VMWARE does a better job virtualizing a machine (which is what NTVDM is supposed to do New Technology Virdual Dos Machine) - a complete windows machine, or Linux machine or DOS box, than does Microsoft, our Multi-Billion dollar software monopoly that is dong all these great things for the public.
Microsoft is the problem, it's their attempt to kill DOS apps, it has nothing whatever to do with what is possible. They could have done a good job, they elected to do a bad job, or they dont' have the requisite skills to do it right, as do the people at VMWARE.
Microsoft XP is simply broken - either by incompetence, or by design, it's your guess.
PS: I only use Windows XP to find problems. I have absolutely no use for it otherwise. I don't suppose "phone home" spying, or Microsoft intrusions, or monopolist apologists who think Microsoft is a saviour.