How to Fix an Invalid Partition Table

All computer data is stored on drives, most commonly hard disk drives. These drives are divided into sections called “partitions.” Most computers have one partition per hard drive. Each partition is treated by the operating system as though it were a separate drive. The properties of each drive’s partitions are stored in a special file called a “partition table.” If the partition table is damaged or missing, the drive will not function properly, and if the drive has the computer’s operating system installed on it, the computer may not boot. Follow these instructions to access Windows 7’s built-in partition repair tools.

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Disconnect or remove all removable or external drives.

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Restart the computer.

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Wait for the BIOS status screen to appear. The screen will either have the logo of the computer manufacturer (such as Dell) or be black with white letters and many technical details.

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Press and hold the "F8" key as soon as the BIOS screen disappears. The Windows "Advanced Boot Options" menu appears on the screen.

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Select “Repair Your Computer,” and then wait for the Windows 7 Recovery Environment to load.

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Select your keyboard layout from the drop-down box.

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Log in using an administrator account, if necessary. The “System Recovery Options” window appears.

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Click “Command Prompt.”

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Type “bootrec /fixmbr” without quotation marks.

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Wait for the process to finish and restart the computer to see if it worked. If it did not work, repeat steps 2 through 8, then continue to the next step.

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Type “bootrec /fixboot” without quotation marks at the command prompt.

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Wait for the process to finish and restart the computer to see if it worked. If it did not work, repeat steps 2 through 8, then continue to the next step.

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Type “bootrec / RebuildBcd” without quotation marks at the command prompt. If the command is not successful, it’s likely that the disk is not recoverable and you will have to format the disk and reinstall the operating system.