Article ID : S500007196 / Last Modified : 11/04/2018

Why does the operating system (Windows) start with an error message?

Applicable Products and Categories of This Article

After starting the computer, the following error messages appear just before the operating system (Windows) starts, and the computer hangs.

- "Missing Operating System"
- "Operating System Not Found"
- "Invalid system disk"


The following messages "Missing Operating System", "Operating System Not Found", "Invalid system disk" may appear on condition that no system files which enable the boot up of Windows are found in the boot disk, or the boot disk is not recognized. The disks which make the operating system boot are the boot disk (HD, FD or CD-ROM).

[Procedure]
(A) Ensure that there is no non-bootable floppy in the drive.

(B) Verify that the hard drive is recognized in the BIOS.
Refer to the Installation Manual on how to access the BIOS. If the hard drive is not been recognized in the BIOS immediately after a new hard drive had been installed, it is not connected correctly or failed to set. Verify the setting once again or set the computer to default to modify the condition.

(C) Ensure the hard drive is recognized using a startup disk (system disk).
1) Turn on the computer with a system disk.
2) When A:\> is displayed, execute the following commands. A:\>C: [Enter]
3) If C:\> is displayed, the hard drive is recognized on the computer. In case it failed to boot from the disk, verify that the boot option is set to boot from the floppy drive in the BIOS Setup Menu.
4) If the hard drive is recognized, system files in the hard drive may be lost. Execute the following commands and restart the computer without the floppy disk. C:\>A: [Enter], A:\>FDISK /MBR [Enter], A:\>SYS C: [Enter]

(D) Verify the boot disk is set active. Execute FDISK and select [Display partition information] in FDISK Options. Verify the [Status] of the drive that has system files is set as "A". In case you set the drive active, select [Set active partition] in FDISK Options and set the drive that has system files active.

(E) Restore the system using System Recovery CD-ROM to install the system to the hard drive. Formatting the hard drive is recommended. Refer to the Instruction Manual on how to restore the system. If none of these counter-measures are helpful, call the technical center for further assistance.