A few suggestions:
DOSBox is a free DOS emulator mostly for games. I have only run the Linux version from a Kanotix (Linux on bootable CD). It ran my ancient Chessmaster 2000 game, which doesn't work in XP. Other options: Use Partition Magic, or QTParted from a Knoppix or Kanotix disk to shrink your ntfs partition and crate a FAT partition to set up a dual boot with DOS or Win9x. Warning: Back up your data if you are going to repartition. If your PC supports booting from USB drives (most newer computers do) you could install DOS on a USB flash drive or external hard drive.