Hardware: Intel i7 2600K (not overclocked, SLAT compatible, virt. features enabled in bios) Asus Maximus IV Extreme-Z (Z68) 16Gb RAM 256Gb SSD Other non-trivial working parts Adding Hyper-V is causing a boot loop resulting in an attempt at automatic repair by Windows 8 after the second or third loop: I'm trying to get the Windows Phone 8 SDK installed and I've narrowed down my troubles to the Hyper-V feature in Win8. This is required to run the WP8 emulator and there are no install options to omit this feature. My first attempt completely borked the OS as I did not have a recent restore point or system image, so I did a completely clean install and made plenty of backups/restore points. I skipped the SDK install and went straight for the windows feature add-on for Hyper-V. This confirmed that Hyper-V is the issue as the same behavior resulted. I cannot find any hint in the Event Logs. Cancelling automatic recovery causes the same behavior to repeat. I don't have any other VM products installed. My only recourse is to use a restore point, try something else, install it again, and see what happens. No luck so far. I'm on my 10th attempt here. Any help would be much appreciated. EDIT: I found a collection of tips here.. http://social.msdn.microsoft.com/Forums/en-US/wptools/thread/b06cc9f2-aa5e-4cb3-9df1-0c273e1dfd68 So i've been attempting various bios settings to resolve this issue with no luck. I've tried setting 'CPUID Limit' to disabled. This seems to work partly as Win8 boots but no USB devices work at all. I also attempted disabling the usb 3.0 controller as the msdn topic lists an issue with USB controllers on Gigabyte boards. This also doesn't work. The USB devices light up but no input is received by the OS. All of my other bios CPU settings are in line with the info in the post. I'm totally stumped. Bios screenshots: http://i.imgur.com/yKN5u.png http://i.imgur.com/Y9wI4.png http://i.imgur.com/F6EuO.png