IBMDOS vs MSDOS problem.

[Dexahol]

This is one of the oddest problems I've seen in awhile. Generally, I'm pretty competent with DOS, but this one has me perplexed. And sorry for this being a bit long-winded. I figured you'ld need all the facts.

We have a laser control system that has an older embedded x86 computer in it. It uses DOS 5.0 as an OS, but since it takes commands from a larger piece of equipment, we can't alter that. We decided to use an old flea-market 486 as a "test" unit. I have the original floppy with minimul DOS 5.0 files on it:

COMMAND.COM
IO.SYS
MSDOS.SYS
FDISK.EXE
FORMAT.COM
MODE.COM
AUTOEXEC.BAT

. . . and then all the laser specific software.

I can boot from that floppy just fine. When I try to do a FORMAT C: /S, I get a "Please insert a DOS diskette in A:" type prompt. This is odd because it booted from this disk. So, I just manually copied the COMMAND.COM, IO.SYS, AND MSDOS.SYS files over. On trying to boot from the C: drive I get:

Can't find IBMDOS or IBMBIO . . . yada, yada, yada.

After doing some MS knowledge base searches I came up with the fact that some older DOS versions used those instead of IO.SYS and MSDOS.SYS. (But 5.0 should use the latter.) Anyway, I typed:

copy msdos.sys ibmdos.com
copy io.sys ibmbio.com

Now the C: drive boots up and runs fine. If you're still with me, that leads to this question:

How can a floppy with MSDOS.SYS, and IO.SYS, format and copy system files that then require IBMDOS.COM and IBMBIO.COM to operate? And I did make sure the floppy didn't have any hidden files on it. All attributes were cleared before proceeeding. This is just the strangest thing I think I've seen in awhile.

Thanks for reading.

Dex

Edit: Some quick last points. Here's the link to the MS knowledge base that says that 5.0 requires MSDOS.SYS and IO.SYS. (Scroll down aways.)

http://support.microsoft.com/kb/q66530/

Also, I typed "ver" and "command" and both report MS DOS version 5.00.