DOS does not start because it cannot find the command interpreter (COMMAND.COM). If this message appears during start-up, either: The COMMAND.COM is not on the hard drive
A COMMAND.COM from a previous DOS version is resident on the disk
A conflict exists between IO.SYS and MSDOS.SYS files.
With DOS 6.0 a user can override the CONFIG.SYS by pressing either the F8 or F5 function keys during boot. This solution only works if the correct COMMAND.COM is in the root directory.
Reboot system with System Boot Diskette. After booting to the A: prompt, type "SYS C:" and press [Enter]. This will transfer the system files back to the hard drive.