Don't Put that MPC formatted disk in the PC!

What happens when you put that MPC formatted disk in your PC.

Well, I have discovered the secret of PC's destroying partition info on MPC2000 formatted drives. Fortunately, the XL model solves this problem, so if you own the XL you do not have to worry about losing partitions when inserting a disk into a Windows PC and this mostly applies to the MPC2000 with explanation how it is fixed in the XL model.

OS's and MPC use the OEM label in the boot sector to decide which other fields in the BPB (the BIOS
Parameter Block) at the start of the boot sector to trust on and which other values to leave alone.
When you insert a disk into a Windows 95+ machine the OEM label is overwritten with a special "IHC" checksum every time you access a floppy (even a simple "DIR a:" with a non-write-protected media
will be sufficient). No other changes are made to the media, however. This OEM label is 8 bytes long and is located starting at byte index 3 on the drive. What does this have to do with the MPC2000? Well, the MPC2000 specifically looks for MPC2000 " To determine if it is an MPC Disk. This also tells the MPC to look in another section to determine the number and locations of the additional partitions on that drive.

Without the "MPC2000 " label the MPC assumes it is just another single partition drive, when in fact, all of the data is still there and intact. There is a fix: Image the drive using a something that accesses the drive below the OS level (like disk2file) and change the OEM label to "MPC2000 " and write the image back to the disk.

This issue has apparently been addressed in the XL. The XL does not depend on reading "MPC2000 " in the OEM field to determine it is an MPC disk, but rather uses some other determination that it is an XL disk and still looks for the additional partition info even if Windows writes to the OEM area. You can even take an MPC2000 disk that has been "damaged" by Windows and load it right up in the XL, even though it would not work on the former model.

I've created step by step instructions on MPC2000 Zip recovery here.