Is it possible to install DOS Ver. 6.22 on XP without reformatting?

There are a number of reasons why that would not be a good idea. 6.22 is extremely limited and will only work on 2Gb or less FAT16 partitions. Check Wengier's responses wrt DOS7 in this post Thinking - it's a habit.

Installing MS-DOS 7.10 over Windows XP will give you dual-boot capacity between DOS and WinXP. The Drive C: should be in FAT32, FAT16 or FAT12 format, not in NTFS format. MS-DOS 7.10 is available from: http://newdos.yginfo.net/msdos71/index.htm P.S. Don't install older versions of DOS on such a system, as jboy said above. --------------- Long Live DOS!