DOS under XP
There are two fundamental ways to run DOS under XP. The default when XP is installed is cmd.exe but thats a funny little scaled-down thing that wont run all sorts of older DOS programs which want to use some of the later extended-memory handling developed during the days of DOS 5.
Try command.com which is much closer to the old DOS-based version underpinning Win98. To do this, change the properties of the start menu entry for 'command prompt' to %system root%\system32\command.com
You'll maybe be surprised to find that the property sheet (once you've done that and XP gets the idea) suddenly has extra tabs which enable you to set many more properties than under cmd.exe
You should also look into the various ways XP offers of fooling Dos programs they are running on an older system. It needs perserverance, but you can usually get most things working. MS knowledgebase also offers lots of help.
The main problem I find is programs which try to run their own colour schemes will find XP wont let them address the hardware and the colours are muddy compromises. MS obviously could solve this simple problem, but they dont want to encourage you to do anything with old software, it doesnt make them any money!