Hyper-V not working on Windows 8

Solution 1:

Hyper-V requires a CPU that supports Hardware Virtualization an it must be enabled in the BIOS. Verify that your CPU supports this (download CPU-z and check). Check the bios settings for virtualization support.

EDIT:

OK, this problem is probably because of an expired or corrupted certificate. Follow these steps:

1. Open up a command prompt and type Services.msc. Go to Hyper-V Virtual Machine Management and stop the service.
2. In the command prompt, type mmc and hit enter. In the File menu, choose Add/Remove Snap-in, select Certificates and then Add.
3. In the next window select Service Account and Next. In the Select Computer select the default of Local Computer then Next.
4. Now under the Service Account drill down to the Hyper-V Virtual Machine Management and select it then Finish and OK.
5. Now in the left hand pane expand Certificates, vmms\Personal and highlight Certificates. In the right hand pane double click on the certificate, should show the Issued To as the host machine name.
6. On the General tab of the certificate at the bottom it should show Valid from and a starting and ending date. The problem is that the certificate has expired.
7. Now close the window for the certificate and then in the right hand pane right click and select delete.
8. Go back to the Services.msc and restart the Hyper-V Virtual Machine Management service.
9. Back to the MMC console and refresh the Personal\Certificates and you should see a new one there. Double click on it and verify the new valid dates.
10. To be able to access the VM's now you will either have to restart the VM or simply use the save state then start the VM back up.