Hyper-V virtual machines do not automatically start on Windows Server 2008 R2 after Reboot

A very annoying issue. However, I was able to find a solution to this.

This problem is related with FSDepends.sys which is probably set to Manual in the Registry. The workaround is to have this driver set to Boot by following the directions below. Only users having expertise in using registry editor should do this.

Make sure that you back up the registry before you modify it. To work around the issue, do the following:

1) Start Regedit.exe.
2) Navigate to the following reg key: “HKLM\SYSTEM\CurrentControlSet\Services\FsDepends”
3) Under the “FsDepends” key change REG_DWORD value “Start” from “3” to “0”
4) Reboot the machine.

For detailed information, visit http://bytesolutions.com/Support/Knowledgebase/KB_Viewer/ArticleId/23/Cannot-start-Hyper-V-virtual-machines-on-Windows-Server-2008-R2-after-Reboot.aspx

Hypervisor is not running on a HP machine

You receive the error message “virtual machine could not start because the hypervisor is not running” in Windows Server 2008 or Windows Server 2008 R2

Just trying to setup a few virtual machines on my new Windows Server 2008 R2 (x64) and I get this error. The machine is a HP Pro 3300 Microtower. After searching on Microsoft Support I found the following article,

http://support.microsoft.com/kb/2490458

which said, The Data Execution Prevention (DEP) setting is not enabled in BIOS. For HP server, it is called “No Execute Memory Protection”

So I entered into the BIOS settings,

1. Press F10 while booting (Computer Settings)
2. Select Security Tab and then sub menu System Security
3. Enable ‘Virtualization Technology (VTx)’. By default I had DEP enabled.
4. If you have another option ‘Virtuialization Technology Directed I/O(VTd)’ – enable that too.

There we go, save changes and boot up. Select the virtual machine in Hyper-V and click Start