Microsoft KB Archive/321626

= &quot;Operating System Not Found&quot; or &quot;Missing operating system&quot; error message when you start your Windows XP-based computer =

Article ID: 321626

Article Last Modified on 11/20/2007

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional

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This article was previously published under Q321626





SUMMARY
When you try to start a Windows XP-Based computer, you may receive an error message that the operating system is not found.



SYMPTOMS
When you start a Windows XP-Based computer, you may receive one of the following error messages.

Error message 1
Operating system not found.

Error message 2
Missing Operating System

When you start your computer to the Recovery Console to recover functionality, you may receive an error message that resembles the following error message:

Setup did not find any hard drives installed on your computer.



CAUSE
This issue may occur if one or more of the following conditions are true:
 * The basic input/output system (BIOS) does not detect the hard disk.
 * The hard disk is damaged.
 * Sector 0 of the physical hard disk drive has an incorrect or malformed master boot record (MBR).

Note Some third-party programs or disk corruption can damage an MBR.
 * An incompatible partition is marked as Active.
 * A partition that contains the MBR is no longer active.



RESOLUTION
To resolve this issue, use one of the following methods, depending on your situation.

Contact your hardware manufacturer
Your best bet may be to contact the manufacturer of your computer or your hard disk. The manufacturer may have a utility that you can use to perform a more detailed scan for damaged areas of the disk and help verify the correct BIOS settings. However, be aware that the damage to your hard disk may be serious. Sometimes this means that your only solution is to replace your hard disk.

If a fix or workaround is not available, you can use the &quot;Advanced Troubleshooting&quot; section to try to resolve this issue.

Advanced troubleshooting
This section is intended for advanced computer users. If you are not comfortable with advanced troubleshooting, you might want to ask someone for help or contact support. For information about how to contact Microsoft support, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/

Method 1: Verify the BIOS settings
Verify the computer's BIOS settings to make sure that BIOS lists and recognizes the hard disk. See the computer documentation or contact the hardware manufacturer for information about how to verify the BIOS settings.

After you verify that the computer's BIOS detects the hard disk, restart the computer, and then test to determine whether the issue is resolved. If the issue is not resolved, or if the computer's BIOS cannot detect the hard disk, you may have issues with your hardware. Contact the hardware manufacturer to inquire about how to resolve this issue. You may have to replace the hard disk.

For information about how to contact hardware manufacturers, click the appropriate article number in the following list to view the article in the Microsoft Knowledge Base:

65416 Hardware and software vendor contact information, A-K

60781 Hardware and software vendor contact information, L-P

60782 Hardware and software vendor contact information, Q-Z

Method 2: Use Recovery Console
Use the fixmbr command in the Windows XP Recovery Console to repair the MBR of the startup partition.

Warning This command can damage your partition table if a virus is present or if a hardware problem exists. If you use this command, you may create inaccessible partitions. We recommend that you run antivirus software before you use this command. We also recommend that you backup your data before you use this command. If the fixmbr command detects an invalid or non-standard partition table signature, the fixmbr command prompts you for permission before rewriting the MBR. The fixmbr command is supported only on x86-based computers.

For more information about Recovery Console, click the following article numbers to view the articles in the Microsoft Knowledge Base:

314058 Description of the Windows XP Recovery Console

307654 How to install and use the Recovery Console in Windows XP

Method 3: Change the active partition
If the partition that is marked as active does not contain the Windows XP startup files, or the active partition is an incompatible or a different operating system, you must first mark the correct system partition as active before you restart the computer. To do this, follow these steps.

Note There can be only one active system partition at a time.  Start the computer to the Recovery Console. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

307654 How to install and use the Recovery Console in Windows XP

 Type Diskpart, and then press ENTER. At the DISKPART command prompt, type List Disk, and then press ENTER.

Note the number of the disk that you want to work with. At the DISKPART command prompt, type Select disk, and then press ENTER.

Note  is the disk number that you want to work with. You should receive a message that resembles the following:

Disk  is now the selected disk

 At the DISKPART command prompt, type List partition, and then press ENTER.

Note the number of the partition that you want to mark as active.</li> At the DISKPART command prompt type Select partition, and then press ENTER.

Note  is the partition number that you want to mark as active. You should receive a message that resembles the following:

Partition  is now the selected partition

</li> At the DISKPART command prompt, type Active, and then press ENTER.</li> At the DISKPART command prompt, type Exit, and then press ENTER</li> Restart the computer.</li></ol>

For more information about how to mark the active partition, click the following article number to view the article in the Microsoft Knowledge Base:

315261 The computer does not start after you change the active partition by using the Disk Management tool

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MORE INFORMATION
For more information about how to troubleshoot startup problems in Windows XP, click the following article number to view the article in the Microsoft Knowledge Base:

308041 Resources for troubleshooting startup problems in Windows XP

Additional query words: windowsxp winxp

Keywords: kbresolve kberrmsg kbprb KB321626

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