So, I did things the MS-recommended way: I booted from a Windows 10 PE (Preinstallation Environment) USB stick that I had to make. To me, that seemed like a silly tradeoff. This works fine, but some people have reported that they then have this extra, old System Reserved partition as a new drive letter in Explorer. Instead, it will shrink the main data partition of your C: and create a new “system partition” at the end of the drive. The other reason is that – as far as I can tell – using /allowFullOS means that MBR2GPT won’t be able to re-use your “System Reserved” partition at the beginning of your hard drive. The reason is that it’s far safer to modify your Windows drive when the Windows on it isn’t actually running. Microsoft itself recommends against doing this!! This allows you to do the conversion from an admin Command Prompt from inside Windows 10.
You probably noticed the /allowFullOS switch. In short, MBR2GPT allows you to convert the boot/partition mojo on your Windows 10 hard drive from MBR to GPT – without reinstalling Windows 10! Hold your horses! You can read all about MBR2GPT on Microsoft’s site, and they even have a nice video to watch.
That’s pretty sucky.įortunately, beginning with the Windows 10 Creator’s Update (version 1703), Microsoft decided to include a tool located here: In the past, you’d have to reinstall Windows. At the bottom, right-click Disk 0, and in the popup menu, see if it says “ Convert to GPT Disk“.If your puter uses UEFI, the next thing to do is to see if your C: is MBR. You can totally screw stuff up if you’re not careful! So, you’re going to need to know if you have UEFI or an older BIOS.įrankly, the rest of this article is not for the faint of heart. To get those faster boot times with UEFI, you really need UEFI on the motherboard + GPT on your hard drive.Totally huge number of partitions are supported – not just 4.Redundant boot/partition info is stored on disk, so GPT is “self-healing”.Totally enormous hard drive sizes supported (like, REALLY big).Just as UEFI is replacing the BIOS, GPT is replacing MBR. It has several limitations, namely only 4 primary partitions are allowed, and the maximum size for an MBR hard drive is 2TB. In other words, the Boot Sector has a Boot Loader that tells Windows to fire up.
The boot loader is a small chunk of code that usually loads a larger boot loader from another partition on the drive. Master Boot Record, or MBR, is basically the boot sector on a hard drive that contains a boot loader for the installed operating system and information about the drive’s logical partitions. So what’s the difference between MBR and GPT? Note the last item above: UEFI supports huge hard drives as long as the drive is using GPT.
Chances are, if your puter is only a few years old, it probably already has UEFI instead of the traditional and outdated BIOS. In short, UEFI is the future of computers – at least when they boot up. Support for ginormous hard drives with GPT.Modular and flexible design for future-proofness.A fancy graphical configuration interface.UEFI, or Unified Extensible Firmware Interface, is like a new version of the BIOS that does more stuff – and better. Once done, it then looks for an operating system to boot, starts it, and then takes a back seat. The BIOS looks at all the hardware in your puter, allocates memory to different devices, and more or less sets up all the hardware to work nicely together. When you power your puter on, it does all kinds of exciting things. The Basic Input Output System, or BIOS, is firmware that sits in a chip on your motherboard. I hadn’t heard anything about it, which is pretty weird considering how awesome it is. It turns out Microsoft has made the process really easy!įirst of all, thanks go to Wingwong for shooting me an e-mail and letting me know about mbr2gpt. Well, okay… First of all, what does all that mean?Īnd second, how on earth do you convert your MBR drive to the new GPT format without having to reinstall Windows? Nowadays, the BIOS is rapidly giving way to UEFI, which provides all kinds of benefits.Īt the same time, hard drives have sort of evolved, so now we’re supposed to use GPT instead of MBR. In the olden days, your puter had a BIOS.