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Microsoft recently released Windows 10 Technical Preview Build 10049 to Windows Insiders on the Fast ring. It is the first release with Project Spartan in it. This build has a known a bug that affects Hyper-V. Microsoft has provided a workaround for it, read it below.
The bug stops us from being able to correctly register one of our system drivers if you choose to install Hyper-V. It should be noted that if you already have Hyper-V enabled, and then upgrade to 10049 – everything works fine. It is only if you install build 10049 and then enable Hyper-V that you will hit this issue.
If you want to use Project Spartan and Hyper-V on the same system – what you need to do is:
1. Install an earlier version of Windows 10
2. Enable Hyper-V
3. Upgrade to 10049
If you are already on 10049 and have not yet enabled Hyper-V, you can either follow the above steps, or hang tight while we work on the next flight!
source:microsoft-news