Help going back from Windows 10 to Windows 7.

Sorry if this is in the wrong forum, but I am in the process of a clean install and could do with some help asap please!

I'm trying a clean install of Windows 7, having upgraded to Windows 10, but experience some annoying bugs.

Anyway, I bought a new PC without an operating system, then an OEM copy of Windows 7 :-/

So, after attempting this clean install, I got to the stage after choosing 'custom install', and where it asks where I want to install Windows. However... there are 3 different partitions, and it say 'Windows cannot be installed' to any of them for various reasons;

Disk 0 Partition 1: System Reserved= (Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks.

Disk 0 Partition 2 = Same as above ^^^

Disk 0 Partition 3 = Same as the first, but with the addition of 'Windows cannot be installed to this hard disk space. The partition was reserved by the computers Original Equipment Manufacturer (OEM).'

So... what on Earth can I do? Format one or all of them? If so, which one/ ones? I really have no idea and would greatly appreciate some help.

Many thanks.


Excellent Member
Microsoft Community Contributor
When you get a GPT or MBR type message that usually means you are trying to install as UEFI to a MBR configured drive or vice versa. An install cannot remove prior partitions on a system so it is best to delete all partitions and install to some unallocated space.

Windows 7 will install as UEFI.
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When you get a GPT or MBR type message that usually means you are trying to install as UEFI to a MBR configured drive or vice versa. An install cannot remove prior partitions on a system so it is best to delete all partitions and install to some unallocated space.

Windows 7 will install as UEFI.

Thanks for the response! Very much appreciated.

I am relatively clueless when it comes to this kind of thing. So I could do with some more detail if possible please.

I was wary of deleting the partitions in case I deleted something important, like the bios, that couldn't then be retrieved. But how would I go about deleting the partitions anyway? I believe there is the option when installing Windows 7. Or should it be done using the bios?



Excellent Member
Microsoft Community Contributor
I can't speak to your personal data. That is your responsibility to maintain. But if you are using a MBR configured drive and try to install in UEFI mode, you will get those messages. You may also run into problems if you install with a previous essential partition already on the drive.

So, when you install you get to a window where you set up the partitions. And you are correct, this is where you select and delete the partitions. If you already have a System Reserved or EFI or small Recovery partition, the system may not install. You need to take the first area of the drive you can and remove all partitions in the area where you want to install the OS. Maybe it is 100 GB or 1 TB, that is up to you, but the install need a clear area where it can create and write to the partitions it needs.

Below is a Disk Management picture of my laptop's MBR install. You would need to delete the System Reserved and C: partitions and install in that unallocated space.

If you are going from an MBR install to a UEFI or vice versa, there can be no partitions on the drive or the install will not be able to convert the drive to the other version.



Active Member
For people configuring their PCs for the first time all by themselves, an error message like “Windows cannot be installed on this Disk” can be a big time problem. One, the message explains little about its cause and second, most of us don’t really have a lot of experience in setting up systems. The problem, however, is not as elephantine as it seems. It is simply a compatibility issue. This problem generally occurs when you try to install windows on a UEFI-based system while your hard drive partition scheme does not support UEFI.

The agreement between the firmware and the hard disk partition scheme is essential for locating the boot loader for the Operating System and hence, is the first step in the installation process of windows on a computer system. By default, recent hardware boot using UEFI mode. Thus, when one tries to use an old hard disk with an updated UEFI-based system, the message “Windows Cannot be Installed On this device” pops up. This is because old hard drives maintain partitions using MBR scheme which is not supported in UEFI-based systems. Therefore, for windows installation it is important to convert either MBR partition scheme to GPT partition scheme or configure the system to boot with the legacy BIOS-compatibility mode.

To solve this problem, you need to convert MBR to GPT disk or enable Legacy boot mode in BIOS. By the way, you can use a freeware AOMEI Partition Assistant to convert disk between MBR and GPT without data loss.


Fantastic Member
Premium Supporter
If I'm reading this right, the conversion from MBR to GPT wouldn't have been necessary as OP could've used the Free Rollback feature in W10 for up to 31 days provided by Microsoft. Your Post was dated 12/1, so you have until Jan. 1, 2016 to do this rollback. As long as you didn't change any hardware such as your hard drive or your Motherboard during this period, W10 could've taken care of this for you without you having to become a disk drive Tech expert. o_O

In any case, it would have been wise to protect all your data on all your Win7 partitions using an Image Clone software compatible with both Win7 & Win10 such as Macrium Reflect or Acronis TrueImage; PRIOR to any rollback as a precautionary measure. AOEMI also has a tool to do this, but has yet to be tested by my company. As Saltgrass astutely put it, your data is your responsibility. Never a good idea to rely on tools, even Microsoft's to protect your data on any kind of OS upgrade or rollback.