I was on a customer call today where they had installed Kapersky anti-virus on their Hyper-V host. The server would no longer boot up. After reviewing KB 961804 I recommended that the customer add the proper exclusions or uninstall Kapersky.  To complicate matters, it was not possible to uninstall the product from Add/Remove programs because the Windows Installer Service does not run in Safe Mode.  Disabling the service did not help either. The final fix was to run the Kapersky removal tool