I can't boot my 486 computern with ms dos, it says "Missing operation system." but i can boot with the dos disk. i tried 'fdisk/mbr',
'a:\sys c:' but nothing works.
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Try installing dos6.22 again. Maybe it helps

Make sure SYS.COM version 6.22 is on the floppy you boot from and that it is a 6.22 boot disk. If the system transfers, the computer almost has to boot unless the hard drive is bad which should give a different error message.

Could that the bios is'nt translating the drive geometry properly.

Your drive may be taking a dirt nap but try the following boot to Bios make sure that the drive is recognised there if not it may be a bad battery, virus etc. correct this then try fdisk.

If not battery or Bios check cable connections, try a different ribbon cable if necessary. Make sure the jumper is set to master.

Try a different HD if it works then your old drive is bad.

Now if you can boot from disk and read the HD now this is a different story.

Make sure your programs are still in the Dos directory do you even have a Dos directory anymore? You may have a virus or accidently wiped out this directory or commands.
Check your Autoexec.bat file some viruses attack this make sure it is reading your PATH correctly. Should read something like Path =C:\dos

hope this helps

Some of the above postings have gone deep somewhat quickly, whereas I would prefer to start off simple.

Once you have booted from your dos disc (presumably a floppy) can you see the hdd and the directories/files that are on it.

If so check out what is missing.

In order to to boot the minimum is three hidden files and COMMAND.COM. I suspect you have somehow deleted this last file from the root directory.

If so, it should also be in the dos directory and you can copy it back to the root.

Good luck - keep us posted.

Hey,

Use FDISK and activate your primary partition first. A formatted harddisk with /s option (or using SYS) doesn't mean that it can boot.