Your Windows and hardware problems solved
My system crashed a couple of weeks ago and refused to boot. After trying to troubleshoot things, I ended up purchasing a new 3TB hard disk and reinstalling Windows 10.
I only realised after the installation that Windows thinks the hard disk is 1.99TB; it doesn’t see the extra terabyte. I downloaded Seagate DiscWizard, but although this can see the extra capacity, it can’t access it. Is there any way of activating the extra space using a software program? Everything I have read online seems to suggest that I need to reformat the hard disk and reinstall Windows, but obviously I’d rather not.
The problem you’re coming up against is a limitation in the master boot record (MBR) partitioning scheme, which dates back to the early 1980s. MBR uses a 32-bit number to keep track of sectors on the disk, and because the sectors are each 512 bytes, that allows for a maximum addressable capacity of ‘only’ two terabytes. The solution is to switch to the newer GUID partition table (GPT) scheme, which doesn’t have this limitation.
There are two problems, however. The first potential issue is that it used to be tricky to convert an MBR disk to a GPT one without data loss. Fortunately, with Windows 10 version 1703 (the Creators Update), Microsoft added a tool to do just this. The other issue arises if you’re planning to boot your system from your 3TB disk. Only computers with a Unified Extensible Firmware Interface (UEFI) support booting from a GPT partition. Most PCs built in the past decade should be fine, but you’ll probably find that, if present, UEFI boot mode isn’t enabled on your system. If it’s supported you should find instructions on how to enable it in your PC or motherboard manual. If it’s not supported, you’ll need to fit a second disk and install Windows on it before you can convert the 3TB disk to GPT.
We’re going to assume that your PC does support UEFI boot mode. Given that you’ve installed Windows on the 3TB disk – and we assume you’ve also saved data
there – we’d recommend taking a full backup before you do anything else. While the backup is running, check that you’re running Windows 10 version 1703 or higher by opening the Start menu, typing winver and hitting Enter. If you’re on an earlier version than 1703, visit www.microsoft.com/en-gb/software-download/
windows10, click Update now and follow the update process. As a final step, open the Start menu, type Disk Management ,and select Create and format hard disk partitions. Look in the left-hand grey boxes at the foot of the Disk Management window to establish the disk number for your 3TB disk; if it’s the only disk, it’s likely to be disk 0.
With your drive backed up and the PC updated if necessary, boot into Windows’ Advanced Recovery Command Prompt by holding down the Shift key while you restart your PC. When asked to choose an option, select Troubleshoot, Advanced options, Command prompt. Allow the PC to reboot and log in when prompted, then at the prompt type mbr2gpt /validate /disk:0, replacing 0 if necessary with the disk number for your 3TB drive. Hit Enter and wait a few moments; you should see the message, ‘Validation completed successfully’. If you do, enter
mbr2gpt /convert /disk:0, again changing the disk number if you need to. The process shouldn’t take more than a few minutes.
Assuming the conversion is successful, you’ll see the message, ‘Before the new system can boot properly you need to switch the firmware to boot to UEFI mode!’. Type exit and hit Enter to restart the PC, then if necessary enter the BIOS and change the boot mode. Once this is done, your computer should boot again, and the disk’s full capacity should be available.
There’s a small risk that the disk conversion won’t be possible or that it will fail. If you do experience a major issue it’s probably best to reinstall Windows from scratch. Provided you do this with your PC already in UEFI boot mode, the Windows Setup program should automatically create a GPT disk, but only if the disk is empty.
With UEFI mode enabled, begin the process of installing Windows, confirming your language settings and the Windows 10 version you want to install, then when prompted choose Custom: Install Windows only (advanced). When asked where you want to install Windows, select any existing partitions on the 3TB disk and delete them until the disk shows only Unallocated Space – be very careful not to delete partitions on any other drives in your computer. Click the unallocated space to select it and click Next, then Windows should install itself to a 3TB, bootable GPT disk.
⬆ Available from Windows 10 version 1703 onwards, the MBR2GPT tool converts MBR disks to GPT