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My system has UEFI, and I want to install both Windows 7 and 8 on a large drive formatted for GPT (I want to also install a few other operating systems, and I need more than 7 partitions).

After installing Windows 7, when I try to install Windows 8, I can't select the partition for installation and I get the message "Windows cannot be installed to this disk. The selected disk is of the GPT partition style."

As far as I understand, I can install one Windows system on each drive, because Windows need to create an EFI boot partition (and an MSR, whatever that is). A second installation will refuse to install if there is already an EFI boot partition.

Is there a way to work around that - except disabling UEFI and using MBR for the drive?

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As far as I understand, I can install one Windows system on each drive, because Windows need to create an EFI boot partition (and an MSR, whatever that is). A second installation will refuse to install if there is already an EFI boot partition.

That shouldn't be the reason. It is quite normal to share a single EFI system partition across several operating systems.

Although I have never tried multiple Windows versions at once – there could be some problems due to both versions storing the bootloader at the same \EFI\Microsoft path – but Win7 and Win8 bootloaders should be compatible.

I get the message "Windows cannot be installed to this disk. The selected disk is of the GPT partition style."

AFAIK, the message has nothing to do with what partitions you have. It shows up specifically because of GPT itself – that is, you booted the install CD in BIOS mode, and Windows refuses to mix BIOS with GPT (nor UEFI with MBR) for its system disk.

(Note that some forum posts claim that the Windows 7 install CD can't boot in UEFI mode, but I'd be surprised if that actually were true...)


I need more than 7 partitions

While the MBR is limited to 4 primary partitions, AFAIK there is no such limit to how many logical partitions you can have inside an extended one...

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    Ah, and, make sure it's 64-bit Windows. The 32-bit version has no UEFI support. – grawity May 13 '15 at 16:22
  • I've booted the install CD in UEFI mode - I've disabled legacy mode in the BIOS and chosen the DVD drive under the UEFI devices menu. Regarding MBR limits, an MBR can define at most 4 logical devices in one extended partition, so the max number of usable partitions is 7: 3 primary + 1 extended that contains 4 logical. – Guss May 13 '15 at 21:37
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    @Guss: Where did you get that "at most 4 logical devices" from? The extended partition table is a linked list. There is no limit to its capacity. – grawity May 14 '15 at 6:58
  • @Guss: As for "chosen the DVD drive", that sounds a bit suspicious. Some firmwares (e.g. Asus) actually list BIOS-bootable devices in the same menu, so if you choose a "device" entry, chances are it will still boot in BIOS mode. – grawity May 14 '15 at 7:04
  • I'm using a Dell. When I said "DVD drive", I meant the entry that listed the model of the drive under the "UEFI" sub-section, and not the entry with the general description "CD/DVD drive" under the "Legacy" sub-section. – Guss May 14 '15 at 8:40
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What you want to do is possible; I've seen posts from people who've done it. I've not done it myself, though.

As grawity says, your error message is a result of your first installation being in EFI/UEFI mode and your (accidentally/mistakenly) booting the second installation in BIOS/CSM/legacy mode. You must learn the procedure to force your system to boot an installation medium in whatever mode you want. This is usually achievable by hitting a function key (which one varies) at system startup to get into the computer's built-in boot manager. With luck, you'll see two options for your boot medium, one of which includes the string "UEFI" and the other of which doesn't. Select the "UEFI" option to boot in that mode and the other one to boot in BIOS/CSM/legacy mode. This procedure doesn't always work, though -- there's no standardization on EFI/UEFI user interfaces, so some implementations do things differently from others and some don't offer critical functionality like this. It's where you should start looking, though. In a worst-case scenario, you may have to jump through some hoops to create a boot medium that supports the boot mode you want to use but not the one you don't want to use.

There's also the question of the EFI System Partition (ESP) and the fact that both versions of Windows will try to place their own boot loader at EFI\Microsoft\Boot\bootmgfw.efi on the ESP. As I understand it, this should work OK, and the Windows boot manager will give you a choice of which version of Windows to boot. (Provided of course you don't accidentally overwrite your first installation when you do the second one.) If you prefer to use something else to select your OS, though, or if you install a third OS and want a single menu to control which OS you boot, you might be better off creating two ESPs so that each version of Windows has its own. This may require temporarily changing the ESPs' type codes so as to force each installer to use the one you intend. Overall, with two Windows versions and nothing else, you're probably better off with a single ESP and let the Windows boot loader present its own menu.

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I had issues at first installing Windows 7 on GPT disk in UEFI. I think the issue was my bios settings...when I went in and made sure the setting for running windows was in EFI mode, and the primary boot device to 'UEFI' version of my disk player, all was fine. (if you are booting from USB this setting doesn't apply, but you need to have windows set to run in efi mode in the bios also)

but now I have Windows 7 & 10 both installed, on GPT disk, in UEFI mode...so it "is" possible. You'll figure it out.

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Windows 7 DOES support GPT boot.

It is possible if you use both 64bit.

But the fast boot will cause the disk be (softwarelly) dirty and make windows 7 do chkdsk. You need to disable it.

You're likely getting the message due to you are using 32bit.

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