I will jump to the conclusions first.
fdisk /mbr ........ re-writes the first 446 bytes of the master boot record.
wrprog.exe ....... add this to the boot floppy. Obtain from PM DOS folder.
FDISK with no other command line options will not alter the MBR if one is detected. See
http://support.microsoft.com/kb/q69013/
FDISK has a slight limitation with respect to NT. See
http://support.microsoft.com/kb/q166454/
FDISK /MBR - Partition Table structure is not altered.
FT (fault tolerance) structures probably do not matter.
Disk signature may matter. I did not research this further. I believe that this occurs as the last 2 bytes of the partition tables at the end of the MBR.
I am a control freak, so I try to anticipate problems and create save points. So consider the following.
The dos command "wrprog /bak track0.dat" saves track 0 from the hard drive with the jumper signifying master to a file a:\track0.dat
The dos command "wrprog /rst track0.dat" write track 0 to the hard drive jumpered as master from the file a:\track0.dat.
ptedit.exe is a dos command available from PM DOS folder, as well. If the disk structures are usable, it will read the MBR for the signature as part of the display for the boot record.
If all else fails, a disk editor gets you down to the byte level. I did not see a likely match in PM DOS folders. Utimate Boot CD has partition tools and a disk editor.
http://www.ultimatebootcd.com
From your previous post, it was not clear if FDISK was used and no change was observed. My post here is pretty well the extent of my knowledge about FDISK. "Fdisk /mbr" restores the small piece of code to interpret the partition table. Since the last partition table shown for this HD is garbage, it should generate some type of error message, or a wild transfer to the wild blue yonder. A disk editor can give a glimpse of parts of these error messages (beginning of track 0).
Some other links from my research:
http://www.apinforma.com/biblio/online/firmware/diskmgr.htm
Ignore window from a.tribalfusion or ignore this link
http://facstaff.uwa.edu/bmoore/340/theBasics/Operations of FDISK The Basics of FDISK.htm
http://www.oreilly.com/pub/h/2290
P.S. Dynamic Disk Overlay (DDO), often supplied by OnTrack or EZ-Drive: I had considered this as a suspect to explain the strange values occuring in the partition table. I would only be guessing at how to confirm this and how to recover.