Question Windows 10 licence install question


Jul 29, 2014

I have a question regarding Windows 10 installs but I am struggling to find the best way to word the issues, so I hope that I have made myself clear – if not, please accept my apologies.

My basic question is… do I actually NEED to have 2 different Windows 10 licences to have 2 different installs on the same PC – 1 for general work and 1 for gaming? I am not referring to the legalities but the actual technical limitations?

The reason I ask is this…

A few years ago I bought a 4770K prebuilt system that came with a Windows 7 Pro 64bit licence. This machine eventually upgraded to Windows 10 Pro. I had 2 separate install of Windows 10 Pro on this machine – one for general work (500GB SATA SSD) and one for gaming (1TB SATA SSD) and this worked great for my purposes. I could install and reinstall on the 2 different SSDs as and when I needed to – everything was wonderful J

Now, I will do my best to explain exactly what happens.

Fast-forward to today and I have recently purchased a new 9900K prebuilt system with 2 x 1TB NVMe SSDs (1 x 970 EVO and 1 x 970 EVO Plus). This DID NOT come with an OS as I had several Windows 7 Pro OEM licences spare and I took a chance that one of these would work with a Windows 10 Pro installer and it does – yay me!

However, if I install Windows 10 on to both of these SSDs only the first install will actually boot the system - the second install won’t boot.

BUT, If I only have one SSD in the machine and install Windows 10 and then physically remove the first SSD and put in the second SSD and install on to the second SSD - then put the first SSD back in to the system as well as the second then both SSDs will be bootable.

This is a problem because if I want to reinstall Windows 10 on one of the SSDs then I have to take the other one out of the system – and this is a PITA because one of the SSDs is mounted under the GPU so that has to come out as well.

Does anyone know why this is the case? Is it because I currently only have one licence “attached” to this machine – bearing in mind my 4770K build that only has one licence and works fine?

As I have another spare Windows 7 Pro OEM licence I could also use that if possible on the second SSD but will that cause any problems having 2 licences attached to the 9900K build? If I need to reinstall one of the Windows setups how will I know which licence number it needs? It would be worth it so that I don’t have to remove drives when I want to clean install Windows 10

Any help and advice you could offer would be very gratefully received.

Many thanks in advance,



I believe the reason the second drive won't be bootable, is the installer is detecting the presence of a boot manager already in place (on the first SSD). Once you've installed to both, independently, you should be able to switch between them at will, without removing the other.

As for the licensing aspect, if you install the same version of Windows, the license should be maintained across each drive (only one is "working" at any given time as a boot drive) - it sees the hardware (not the drive), and no matter which SSD you boot from, you have the same hardware.

However, I'd question two things.
  1. Why do you need a separate OS for gaming vs work?
  2. Why would you need the OS to be activated on both drives, assuming for some weird reason the license went unactivated when booting from one drive, what's the harm?
You can turn your SSDs on and off from bios or change the boot order so it will boot from whatever drive you want,as a matter of fact your bios has a boot menu where you can choose which disc you want to boot from each time you boot.

If you want you can get the free version of easyBCD and add the other windows 10 install to each disc's boot menu so you can choose which OS to boot into from the windows menu no matter which disk you boot from.


Why even bother separating the OS setups that way? Install it once, use it for whatever you use it for. It's a bit like people setting up 8 partitions on their drives, movies, movies i like, shows, videos, music, rap music, rock music, etc... Just put it all in one spot, things are all indexed and search and shortcuts anyway now, and have been for years.

Only thing you need to worry about is backups of the files.


With having 2 identical, bootable, OS's in one system, I've seen far too many instances where it goes wrong.

Win 7 and Win 10? Sure.
Windows and Linux? Sure.
2x Win 10? Why?

Whatever software you're using for work does not affect any gaming performance.


However, if I install Windows 10 on to both of these SSDs only the first install will actually boot the system - the second install won’t boot.
This is because the all boot information lives on the first drive.
The only real way to get around this is to have the drives physically disconnected when you install. Then, you can (probably) choose which to boot from when you power up, and interrupt the boot process. Telling it which physical drive to boot from.