MS-DOS not start

[michaln]

The values correspond to the disk geometry, i.e. how many cylinders, heads, and sectors per track a drive has. Whether that corresponds to the real physical disk layout of the original disk (how many platters, read heads, etc. it has) or not isn't important. What matters is that the parameters of the virtual disk match what the software installed on it expects.

This is actually a good example of why raw disk images are troublesome -- there is simply nowhere to record the disk geometry. A VMDK or VDI file can record the geometry and can present the right values to the emulated hardware when attached to a VM.

I used Norton DiskEdit from Norton Utilities 8.0, now a 20+ year old utility, running from a boot floppy image in a VM with the original VMDK attached. It's possible to do without, just by looking at the raw disk image, but that's more work. DiskEdit nicely formats the partition table in the MBR (Master Boot Record, the first sector on the disk) as well as a DOS-style boot sector. With a straightforward disk layout like yours (single partition), the partition table is enough to look at. It shows the maximum cylinder, head, and sector per track values. The DOS boot sector shows the number of sectors per track and heads, and the number of cylinders would have to be calculated manually.

The first thing though is probably recognizing that a small disk (40MB) is almost certainly going to have an "old" geometry not compatible with gigabyte-sized drives, and knowing that it matters.

[Twin]

OK I will educate myself
Thank you very much !!!