In Windows systems, the Disk Management is a snap-in that is provided with the Microsoft Management Console (MMC) module. This utility enables you to manage the system disks such as creating or deleting partitions, marking partitions as active, etc. However, sometimes when you mark a partition as active the system may not be able to boot. This may happen because of various reasons. There are various methods that you can perform to resolve this situation. However, if these methods are not able to address the situation in the desired manner then you should use a partition recovery software to do so.

Consider a scenario wherein you have a Windows 2000. You have marked the primary partition as the active partition using the Disk Management utility. However, the marked partition does not contain the essential boot files. So, when you start the computer it fails to boot. An error message is displayed, that is:

"NTLDR is missing"

Cause: The root cause of this situation is that the marked active partition does not have the boot files, which is why the system is unable to boot.

In the Intel-based systems, the marked active partition should be a primary partition that must be located internally on the disk. And, there must one and only one active system partition at one point of time. In case, you need to use another operating system then you should mark its system partition as active before you restart the system. Usually, the boot files include ntldr, ntdetect., and boot.ini.

Resolution: To resolve this problem, you should perform any of the following methods: You should change the active partition using a floppy disk to boot and then using the disk utilities to manually change the active partition.

You should look to install another Windows instance in a parallel location, provided there is enough disk space. After the installation, you should change the active partition using the Disk Management utility.

You should enter the Windows Recovery Console to use the fixboot command to make the active partition as bootable. After booting the system, you should change the active partition from the Disk Management utility. Restart the computer and find that the system is working fine now.

If you are still not able to boot the system, then you should use a third-party partition recovery software to restore the trapped data. Such read-only tools possess rich user interface using which you can easily recover partition.