Does your computer have multiple partitions with different operating systems? If so, you can change the active partition in Windows so that the correct operating system is loaded when the computer starts. This is called a dual or multiboot system.
Changing the active section is quite a tricky task, so if you plan on doing it, you probably don’t need the explanation above! Change the active partition only if this partition contains an operating system, otherwise you will have a non-working computer.
In addition, there are a few things to note about marking a partition as active:
- A logical disk or extended partition cannot be marked active, only primary partitions can be made active.
- There can be only one active partition on a physical hard disk. Trying to do it differently will cause all sorts of problems.
- If your computer has multiple physical hard drives, you can mark the partition as active on each drive, but only the active partition on the first hard drive detected by your BIOS will start the computer. You can enter BIOS and change the order in which hard drives are detected.
In addition to the above notes, additional steps must be taken to boot the system. Simply setting a partition as active does not guarantee that the system will boot correctly.
- The active partition must have a boot sector created by the operating system.
- The active partition must contain the boot loader and boot files for the OS and must know the location of the OS on the physical hard drive.
- The actual operating system must be located in the correct location on the hard drive
When the computer boots up, it first looks for the active partition on the primary partitions. The boot sector located at the beginning of the active partition will launch the boot loader, which knows the location of the operating system boot files. At this point, the operating system will boot and start.
Set the active partition via Disk Management
Open Computer Management by going to Control Panel, clicking System and Maintenance and then clicking Administrative Tools.
You can also click Classic View and then select Administration. Now click on “Disk Management” in the “Storage” section.
Another option is to go to your desktop, right-click Computer or This PC, and select Manage. You will see Disk Management in the menu on the left as shown above. Right-click the primary section that you want to mark as active and select Mark Section as Active.
Set the active partition via command line
If you screw something up in Windows and mark the wrong partition as active, you will no longer be able to boot your computer. If you cannot mark a partition as active with Windows, you need a command prompt.
Depending on your version of Windows, command line access can be a bit tricky. Read my post on Restarting Windows in Safe Mode to access system recovery options for Windows XP, Vista, 7, 8, and 10. If you are using Windows 8, read my post on booting with system recovery options. Once there, you need to go to the Troubleshoot section, then Advanced options and then click Command Prompt.
First, enter a command prompt from your boot disk and type diskpart at the command prompt.
At the DiskPart command prompt, enter a list of drives. You will see a list of drives connected to your computer. Now enter select disk n, where n is the disk number. In my example, I would type select drive 0.
Now that we have selected the correct drive, enter the partition list to get a list of all partitions on that drive. To select the partition we want to make active, enter select partition n, where n is the partition number.
Now that we have selected the drive and partition, we can mark it as active by simply typing the word “active” and pressing Enter. This is it! The baffle is now installed.
Most people are familiar with using FDISK to mark a partition as active, but this is an older and outdated command now. DISKPART should be used to manage disks and partitions on a modern Windows computer.
Set the active partition via MSCONFIG
In addition to the above two methods, you can use MSCONFIG to set the active partition. Note that this method only works for primary partitions on the same hard drive, since MSCONFIG does not detect partitions on other hard drives. In addition, only Windows can be installed on another partition to make it active.
If you are not familiar with the MSCONFIG tool, read my previous tutorial on using MSCONFIG. Open MSCONFIG and go to the Download tab.
You will see a list of operating systems, and the Current OS will be active; Default OS after the operating system name. Click a different operating system, and then click Set as default.
There are other methods of setting an active partition, such as using a Linux Live CD, but they are much more complicated and usually unnecessary. Even if the built-in system recovery options do not allow you to access the command line, you can always use a secondary computer to create a bootable USB recovery drive. If you have any problems, do not hesitate to leave comments. Enjoy!
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