virtualbox.org

we get the error
VT-x is Not available
after installing Windows Phone SDK

Hyper-v is not compatible with any other virtualizer. It claims complete control of VT-x and does not allow sharing.

I am getting the same thing after installing the Visual Studio Community Edition along w/ the Windows Phone SDK + Emulator. I didn't put 2 and 2 together. I removed the Windows Phone emulator, but no luck. Any solutions?

This is really a Micorsoft question, but here is a link on how to disable Hyper-V http://answers.microsoft.com/en-us/wind ... 41e58067ab

Hyper-V is not listed in 'Turn Windows features on or off'. I've uninstalled Windows phone emulator, restarted, made sure virtualization is enabled in BIOS, made sure Hyper-V is not running, uninstalled Virtualbox and reinstalled, still nothing. Not sure what else to do.

It's hard to say what your issues is without actually touching the machine but if you have enabled hardware virtualization in the bios and it is still not available to VirtualBox you need to find what is using it. Aside from the obvious Hyper-V some debuggers and Virtual software has been know to capture VT-x as well as trying to run nested ( virtualizer in another virtualizer).

Ok, after a lot of googling I've figured it out. I had to disable "Execution Prevention" in my bios to get everything back to normal. Not sure how it got set to begin with, but I can see 64-bit Guest OSess now.

Disabling "execution prevention" would not enable you to run 64bit VMs, but if messing with the BIOS involved powering down and rebooting the host then that was probably the actual fix.