|I'm not familiar with DM so can't help yoiu with it. You might boot with the bootdisk again and at the a:\> prompt type FDISK/MBR and enter.|
If that doesn't work you can check this google search:
and see if you find something to your liking. It's possible someone else will post in with better software suggstions.
I assume you want to recover whatever is on the drive. However, if you just want to wipe the drive and reinstall an OS you may be able to delete the existing partition(s) and then repartition, format and install an OS.
The mantra of the aging hippie--"Power to the government, right on"