It's been a while since I've worked with pure DOS apps under Windows XP. But if I recall correctly, most DOS apps are written with the assumption that they're on a single-user single-task operating system (DOS), on which it has all the CPU, memory, etc, at it's disposal.
Windows, in that way, needs to deal with that to be able to run those programs. So in essence, it has to be able to manage how those programs operate, especially if they are left running over time. Since most DOS programs will use up 100% (or close to) of the CPU when it just sits and polls the keyboard (or other devices) for responses, Windows needs to try to detect that and throttle back the CPU it receives (in addition to the memory it gets too, since most DOS apps will grab whatever they can get with the assumption that they HAVE everything).
Your options:
1) Find a Windows version of this app.
2) Install a copy of DOS in a virtual machine (VMWare or Microsoft Virtual PC) and run it on that.
3) Try an emulator like DOSBox.
