Updated: April 27, 2010

Applies To: Windows Server 2008 R2

This topic is intended to address a specific issue identified by a Best Practices Analyzer scan. You should apply the information in this topic only to computers that have had the Hyper-V Best Practices Analyzer run against them and are experiencing the issue addressed by this topic. For more information about best practices and scans, see Best Practices Analyzer.


Operating System   Windows Server 2008 R2
Product/Feature    Hyper-V
Severity    Warning
Category     Prerequisites


Windows hypervisor is not running.


Virtual machines cannot be started until Windows Hypervisor is running.


Check the Windows Server catalog to see if this server is qualified to run Hyper-V. Next, make sure the BIOS is enabled for hardware-assisted virtualization and hardware-enforced data execution prevention. Then, check the Hyper-V-Hypervisor event log.
To check the catalog, see Windows Server catalog (http://go.microsoft.com/fwlink/?LinkId=111228), and then search for “Hyper-V” as an additional qualification.
Hyper-V: Windows hypervisor must be running_Hyper-vCaution
Changing certain parameters in the system BIOS of a computer can cause that computer to stop loading the operating system, or it can make hardware devices, such as hard disk drives, unavailable. Always consult the user manual for the computer to determine the proper way to configure the system BIOS. Also, it is always a good idea to keep track of the parameters that you modify and their original value so that you can restore them later if needed. If you experience problems after changing parameters in the system BIOS, try to load the default settings (an option is usually available in the BIOS configuration utility), or contact the computer manufacturer for assistance.

To verify virtualization support in the BIOS

  1. Restart the computer and access the BIOS. The system BIOS can usually be accessed by using a configuration utility that is available during the initial boot process of a computer. Immediately after you turn on most computers, they will display for a few seconds the key or combination of keys that you need to press to access the configuration utility.
  2. Locate the parameters for virtualization and hardware-enforced Data Execution Prevention (DEP) and verify that they are enabled. The following are common locations for these parameters in the menu of the configuration utility, and some examples of what they might be named in the BIOS:
    • -Virtualization support:

      • >Usually available under the settings for the main processor or performance. In some cases, it might be available under the security settings.
      • >Look for parameter names that include “virtualization” or “virtualization technology”.
    • -Hardware-enforced DEP:

      • >Usually available under the security or memory settings.
      • >Look for parameter names that include “execution”, “execute”, or “prevention”.
  3. If necessary, enable the settings by following the instructions in the configuration utility. Save the changes and exit the utility.
  4. If you made any changes to the BIOS, turn the power off and then turn it back on to complete this process.
    Hyper-V: Windows hypervisor must be running_hypervisor_02Warning
    We recommend that you turn the power off and then back on (sometimes called a power cycle) because changes to the BIOS do not take effect on some computers until this is done.
Next, check the Hyper-V-Hypervisor event log. If there are problems, check the System log for event source “Hyper-V-Hypervisor” for details.

To check the System log for Hyper-V Hypervisor

  1. Open Event Viewer. Click Start, click Administrative Tools, and then click Event Viewer.
  2. Open the Hyper-V-Hypervisor event log. In the navigation pane, expand Applications and Services Logs, expand Microsoft, expand Hyper-V-Hypervisor, and then click Operational.
  3. If Windows hypervisor is running, no further action is needed. If Windows hypervisor is not running, perform the following steps.
  4. Open the System log. (In the navigation pane, expand Windows Logs and then select System.)
  5. Look for events from Hyper-V-Hypervisor for more information. For example, event ID 41 indicates a problem with the BIOS configuration: “Hyper-V launch failed; Either VMX not present or not enabled in BIOS.” (To filter for these events, from the Actions pane, click Filter Current Log, and then for Event sources, specify “Hyper-V-Hypervisor”.)

Additional references

A video is available that demonstrates how to change the BIOS settings on your computer to make the Windows hypervisor run. To view the video, see Hypervisor is not running error: How to fix (http://go.microsoft.com/fwlink/?LinkId=163578).