I don't understand. I did a third try and ms-dos booted (I mean from the hard). And I didn't touch anything. I had even turned off the machine with no results. And now ms-dos happens to boot!
But this is worse than before. I thought something was bad in the MBR. And and it was only a matter of fixing it. But now it may be the hard disk is having I/O errors. In any case it seems to be an intermitent failure, which are very hard to detect. Well, it's not so bad, because still the data remain accessible. The only issue is I cannot boot in ms-dos and, therefore, I cannot run some programs that only run under ms-dos, specially a chess program named chess.exe (the only one in fact). And also, of the four o.s., ms-dos 5.00 is by far the fastest. Regards.
In my machine (PC IMB-compatible deskop) I have two hard disks installed. Both are attached to the primary (that is, IDE-0), one as master, the other as slave. On the master one (I'll call it HD1) I have two partitions with GNU/Linux kernel 2.6 on one and Windows XP on the other. On the slave one (I'll call it HD2) I have two partitions with MS-DOS Ver 5.00 on one and Windows 98 on the other.
In the BIOS setup, I have the following settings:
1st Boot Device = Floppy
2nd ----------- = Disabled
3rd ----------- = IDE-0
Try other boot devices = yes
O.K.: it is about two years that I've been able to boot either of the four O.S. with exactly the configuration described above, including the BIOS setup.
But today, when trying to boot ms-dos, I got the message "Non system disk or disk error". And I don't have a floppy inserted, nor a cd-rom in the cd-rom drives nor a usb flash-memory pluged in.
On the other hand, the partition and its file system (ms-dos I mean) is accessible to all of the other O.S., which keep booting perfectly well.
What can be the issue here? Well. Any hint would be welcome and thanks in advance.