Windows Vista boot sequence first involves loading the MBR, followed by the drive boot sector . The boot sector then accesses the Windows Boot Manager to finally load the Boot Configuration Data (BCD) store and complete loading the operating system. If any of these components get corrupt, the Windows fails to start. As a result, your data becomes inaccessible. The first tip to solve such problems is to run 'Startup Repair' If this fails, you should repair them manually or reinstall Windows as the last resort. At this point, if a valid backup is unavailable, a Partition Recovery Software can get your data back.

For example, suppose you use a Windows Vista based computer. You receive a blue screen error message when attempting to start the computer. The error indicates that a critical boot data structure (MBR, boot sector or Boot Configuration Data store) is corrupt. When you try to boot the computer from Vista installation disc and use 'Startup Repair' option under 'System Recovery Options' from Windows RE (Recovery Environment) as the basic troubleshooting step, you get an error message as below:

“Operating system: Unknown on (Unknown) Local Disk”

The data stored on the hard drive is inaccessible.

Cause

The 'System Recovery Options' cannot repair the disk. The error occurs when this fails to locate the operating system automatically.

Solution

Since the 'Startup Repair' has failed, you need to repair the corrupted boot components manually. To do so, you should use Bootrec.exe tool of Windows RE. You should first examine the primary boot time error message and error details after running 'Startup Repair' to know the exact component causing the problem. After this, you can apply these steps:

Boot your computer using Windows Vista installation disc and choose 'Repair your computer' option Open the command prompt under 'System Recovery Options' after selecting the target operating system Type 'Bootrec.exe' and use any of the following options on the basis of affected component:

/FixMbr /FixBoot /RebuildBcd

If the above measures do not solve the existing issue, you can reinstall Windows provided a complete backup is available. If not, you are recommended to use a Partition Recovery utility to recover the lost data.. A Partition Recovery Software can extract lost and missing data using high-end scanning algorithms, while providing a self-explanatory interface.

Stellar Phoenix Windows Data Recovery is a reliable and powerful hard drive recovery software that recovers lost partition, deleted partition recovery and inaccessible data . The advanced Partition Recovery application is compatibile with Windows 7, Vista, XP, 2003, and 2000. The tool provides a set of impressive features such as, disk cloning, disk imaging, drive status, RAW file recovery, and more.