The DOS partition could easily be the backup/restore partition your vendor cd installs to let you recover/repair if you have a Dell or HP unit...or it could be the small partition that Compaq's used (may still for all I know) that gave you access to your bios for making changes to it.
Deleting the partitions is fairly easy with Delpart.exe (it runs from a regular bootdisk with the program included or you can boot with your bootdisk and then switch floppy disks if delpart is on a separate disk). Once you run the program and delete the partitioning, you can then use your XP cd to boot with (make sure your bios is changed to have the cdrom be the first boot device) and XP can create and format new partitioning and install windows.
LOCATION OF DELPART.EXE
http://www.bootdisk.com in the Utilities area or HERE
Extract the file to a floppy disk, boot up with your windows bootdisk, change to this floppy disk and run Delpart.exe and you can remove all partitioning.
How do you get a rid of a partition? I was trying to use fdisk to remove 2 existed partitions, a dos and an extended dos partition? the primary one can be remove but not the extended one?. The message said: can not delete extended dos partition while logical drive existed? so I try to delete logical drive first?. The computer is telling me it no logical drive is defined and also on the bottom: all logical drive deleted? When I try to use the CD that came with the Dell to reload the OS?(windows XP) it is telling me ?error loading operating system? so what should I do?

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