Non-System Disk

Non-system disk

If the computer says “Non-system disk or disk error”, the computer is having trouble finding the hidden system files. (In MS-DOS and modern Windows, the hidden system files are called IO.SYS and MSDOS.SYS. In PC-DOS, the hidden system files are called IBMIO.COM and IBMDOS.COM.)

Those hidden system files are supposed to be on your hard disk. You can get that error message if those hidden system files are missing from your hard disk — because you accidentally erased those files, or a virus erased them, or your hard disk is new and not yet formatted, or when you formatted the disk you forgot to put “/s” at the end of DOS’s format command (or forgot to put a check mark in Windows format’s “Copy system files” box).

A more common reason for getting that error message is:
you accidentally put a floppy disk into drive A! When the computer boots, it looks at that floppy disk instead of your hard disk, and gripes because it can’t find those system files on your floppy disk.

Cure:

Remove any disk from drive A. Turn the computer off, wait until the computer quiets down, then turn the computer back on. If the computer still says “Non-system disk or disk error”, find the floppy disks that DOS or Windows came on and try again to install DOS or Windows onto your hard disk.

Command interpreter If the computer says “Bad or missing command interpreter”, the computer is having trouble finding and using your COMMAND.COM file. That file is supposed to be in your hard disk’s root directory — unless your CONFIG.SYS file contains a “shell=” line that tells the computer to look elsewhere.

Probably you accidentally erased COMMAND.COM, or a virus erased it, or you tried to edit it, or your COMMAND.COM file came from a different version of DOS or Windows than your hidden files, or you accidentally put a floppy disk in drive A (which makes the computer look for COMMAND.COM on your floppy disk instead of your hard disk).

Cure:

Remove any disk from drive A then try again to boot. If you get the same error, put into drive A the main floppy disk that DOS or Windows came on, and reboot again. (Make sure you use the original floppy, not a copy. Make sure you use the same version of DOS or Windows as before; don’t switch versions. For DOS 4, insert the disk labeled “install”; for DOS 5 or 6, insert the disk labeled “setup”; for modern Windows, use whatever combination of floppy disks and CD-ROM disks your manufacturer gave you for “recovery” or “setup” or “boot”; if a disk says “upgrade”, that disk isn’t bootable and you must find a different disk instead.)

Then try to copy DOS or Windows onto your hard disk again.

If you accidentally erased COMMAND.COM from your hard disk, you might have also erased CONFIG.SYS & AUTOEXEC.BAT and need to reconstruct them.