GPT vs MBR: Which hard drive format for Windows 8.1?

If you're building a Windows 8.1 PC you'll need to properly format the hard drive. So which format - GPT or MBR? 

A reader wrote into Helproom to ask: "I’m building a new PC for use with Windows 8.1 and when it comes to formatting the hard drive, I have the choice of using MBR format or GPT format. Which should I use and why?" Also see: What's the best portable hard drive 2014 

This is how we answered their question. (See also: Recover deleted files for free: recover lost data.)

GPT or MBR? 

Master Boot Record or MBR format has been in use since the early 1980s and is widely supported, though, it’s limited to a maximum of four primary partitions with up to 2TB, a size that’s easily exceeded by many large hard drives available today.  

The GUID Partition Table (GPT) format, is a newer technology which allows much larger disks to be used up to a theoretical limit of 9.4 zettabytes (ZB), or nearly 10 billion terabytes. It has been estimated that, as of 2013, the whole of the world wide web occupies around 4ZB. Windows currently limits GPT partitions to 256TB.  

Additionally, there’s no theoretical limit to the number of partitions you can create on a GPT format drive. 

The main issues to consider are those of compatibility. Older versions of Windows, such as 32-bit XP can’t read, write or boot from GPT disks. Newer desktop versions of Windows can handle the disks quite happily, but require you to have a modern PC which supports UEFI on the motherboard. 

If you’re using MBR format, you may also run into problems when installing multiple operating systems on a single drive. Obviously all installed operating systems must be compatible with your chosen format, but it’s also not unusual for an operating system to create multiple partitions during installation, especially if you want to install a recovery partition. Using a GPT drive should ensure that you don’t run out of available partitions. 

Another advantage of GPT over MBR is that is saves two copies of the GPT header, one at the start of the disk and one at the end. This small amount of redundancy affords some protection against data corruption when compared to MBR format which only saves a single partition table. 

So, to summarise: if you want to use a large hard drive with lots of partitions and multiple operating systems, go for GPT. 

If you want to retain compatibility with older hardware, you can stick with MBR. 

Still stuck? Ask for advice in our Tech Helproom forum.