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I have a dual-boot system, Windows 7 on my C: drive and Server 2008 R2 on my K: drive. Two separate hard drives.

I set up Hyper-V and everything was running great, building VMs left and right and loving life. My Win7 drive became corrupt and i blew it away and reinstalled windows 7. In my Server env, I couldn't start any VMs because "hypervisor is not running". I ran bcdedit /set hypervisorlaunchtype auto and that fixed my problem.

I booted into Windows 7 and used that for a few days. No problems. Booted into Server 2008 R2 today and I get the same error

"The virtual machine could not be started because the hypervisor is not running."

No recent messages in the Hyper-V-Hypervisor Operational log. Only recent error in the Hyper-V-VMMS Admin log is following:

'Hypervisor' driver required by the Virtual Machine Management service is not installed or disabled. Check your settings or try reinstalling the Hyper-V role.

I don't see any other relevant messages in other Hyper-V-* event logs.

I checked the %systemdrive%\ProgramData\Microsoft\Windows\Hyper-V\Virtual Machines\ folder and it's chock full of symlinks to virtual machine config files, which one blog entry mentioned as a possible issue.

I'm at my whit's end, not sure what else to do. Virtualization is enabled in BIOS, relevant services are started, etc. Any ideas?

Resolution:

I had to re-apply the set hypervisorlaunch flag, and then I turned my machine off and physically unplugged the machine's power supply and then rebooted. Hypervisor worked fine after that. This is a consistent fix. If I just re-apply the flag without unplugging, it doesn't work. I must say, I dread booting into Win7.

Think my problems will go away when Windows 8 comes out w/ Hypervisor on the client OS?

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migrated from serverfault.com Dec 5 '11 at 22:29

This question came from our site for professional system and network administrators.

4  
Have you tried reinstalling the Hyper-V Role? –  ErnieTheGeek Oct 12 '11 at 19:41
1  
Please add the result of the command bcdedit to your question. –  Ricardo Polo Oct 13 '11 at 2:43
1  
This question is suitable for Super User, and the Server Fault moderators have informed us that we should not migrate it back. Let's try to focus on solving Nathan's problem, and not generate any more controversy. This question is a good fit here. –  nhinkle Dec 17 '11 at 21:37
    
@RicardoPolo: From what I have read the hypervisorlaunchtype is removed every time Windows 7 is launched, although he hasn't clearly specified whether he tried the bcdedit /set ... command again. –  Tom Wijsman Dec 21 '11 at 14:11
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1 Answer

up vote 3 down vote accepted

In the spirit of Science - it works, bitches, I just tried this, by dual-booting away from Windows Server 2008 R2, and it looks like when you install the other OS, it goes and disables a few of the extra flags in the bcd store.

When you're in 2008 R2, run the following from an elevated command prompt:

bcdedit /set hypervisorlaunchtype auto

This should put the Hyper-V driver back into the launch procedure and you should be able to start your VM's again.

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This has already been mentioned in the question. Or do you mean that he should try it again? Thinking of which, if running it again fixes it again he might be able to solve this with a boot / logon script though... +1 –  Tom Wijsman Dec 21 '11 at 14:07
    
@TomWijsman - when I tried it, the flags kept overwriting eachother. Also from the reserach I did for this question, that seems to be the only way to fix it. So something weird is going on. –  Mark Henderson Dec 21 '11 at 19:25
    
I think this is the solution, but I gotta tell you I'm not really pleased about this "work-around"... –  Nathan DeWitt Dec 21 '11 at 20:47
    
@NathanDeWitt - to be honest, dual-booting a hypervisor is an incredibly rare and odd thing, it's about as edge case as you can get. –  Mark Henderson Dec 21 '11 at 21:00
    
@Farseeker - in the developer world, it's more common than you'd think. We do SharePoint development, and need Server 2008 vm. but we also do mobile app dev, and it's nice to run on a client OS. yes, we could virtualize the client OS, but that uses resources unnecessarily. running on a laptop, RAM is scarce. dual-booting is a way around it. Booting to VHD is a possible work-around, one I'm looking into. –  Nathan DeWitt Dec 23 '11 at 4:28
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