Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I know that UEFI provides for much faster boot up speeds, but as of right now it is disabled in my BIOS. Should I enable it and it'll switch over auto-magically?

share|improve this question
Check your assumption – Joel Coehoorn Dec 18 '12 at 2:47

Firstly: note that while UEFI can provide faster boot times, it doesn't automatically do so; it depends on the firmware in question.

Secondly: yes, you need to reinstall Windows if you want to switch to UEFI. Windows is installed in UEFI mode only if you boot the install DVD in UEFI mode. You may also need to reformat the disk, because in UEFI mode Windows requires GPT partitions.

(Or, at least, that's how it worked with Windows 7. I wouldn't expect this to have changed in Windows 8 but I can't be certain.)

share|improve this answer
It's easy to convert MBR disks to GPT (although I'm not sure if Windows can do it non-destructively, or if a Linux CD will be needed). – grawity Dec 18 '12 at 8:05

This article describes how to convert a BIOS-mode Windows installation to boot in EFI mode without re-installing. I'm afraid the procedure is a bit too long for a full summary here, but basically it involves backing up your data, converting the partition table from MBR to GPT non-destructively using GPT fdisk, adjusting your firmware settings, creating an EFI System Partition (ESP), and installing the Windows boot loader on the ESP.

share|improve this answer
Do you know if I can somehow create/copy the EFI bootloader files manually, as in part 3.5.2 of the guide you linked: copy the contents of the EFI subfolder of the Boot folder...". My Boot folder does not have EFI – varesa Jan 24 '13 at 23:18
That link is now a 404. :( – Aaron D. Marasco Jan 31 at 17:23
Try this blog post instead. Alternatively, you can use the Internet Wayback Machine to locate an archived version of the original -- specifically, it's archived here. You can see snapshots on various dates. The closest to the one when I first answered the question is here. – Rod Smith Jan 31 at 17:26

While both Rod's and Harry's answers are correct, I think they miss on the benefits of having a UEFI-installed OS (at least Windows 7 and later, I can't speak for Linux).

If you boot your Windows install media (typically USB-flash drive) under UEFI, and install Windows on a GPT partition, you will not only experience faster boot times, but have the ability to use this HDD or SSD on a completely different motherboard, i.e. unplug your hard drive and boot up on another PC, if it supports UEFI boot.

If your current OS is installed as an EFI system, then enabling UEFI boot, won't change anything- your computer won't detect a partition with a UEFI bootloader and probably fall-back on legacy boot.

There's also a high chance that your disk partition is an MBR partition, so in the event of you wanting to ever install your OS as a UEFI system you'd have to delete the partition (formatting won't do it), and create a new GPT partition.

share|improve this answer
UEFI doesn't automatically make the operating system universal. Windows will still need to install appropriate device drivers for the new hardware. – Harry Johnston Mar 12 '15 at 23:24
@HarryJohnston, that may be true, but that usually lasts (in my experience) from half a minute to two minutes. It mostly installs the bare 'plug and play' drivers that merely allow you to use your computer in half its capacity and install the exact drivers you want- sometimes it even downloads those asynchronously in the background, but that's another topic. This is what it looks like when carrying a Win 7 UEFI drive to another configuration:… – Goran_Mandic Mar 13 '15 at 10:34
How is that different from moving an MBR disk with Windows on it from one motherboard to another? – Harry Johnston Mar 13 '15 at 21:36
In my experience (I don't do this for a living, but I've installed various versions of Windows, since 95, at least a hundred times by now, on all sorts of hardware) and have NEVER been able to simply swap hard drives from one PC to another, and not from lack of trying. If you've been able to do it, it might have been some off-shot where the firmware was similar enough. I think EFI wasn't designed with this scenario in mind, and that UEFI changes that. If you have any sources or literature that may prove me wrong, please post them- I love being wrong, it's the only way to learn. – Goran_Mandic Mar 14 '15 at 16:27
It's usually worked for me, except when switching between IDE and SATA models - and even that can be fixed without too much trouble. Mind you, I mostly work with various Dell models. If a motherboard uses a non-standard disk controller that would certainly present a problem, and perhaps this is more common than I realized. – Harry Johnston Mar 14 '15 at 21:31

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .