virtualbox.org

Hello everyone,
I am using Windows 8 Pro 64bit. I have installed Oracle VirtualBox 4.2.10 64bit. Whenever I try to start any guest OS 64bit operating system I get the error that "VT-x features locked or unavailable in MSR" (check attachment error2.jpg). Now I have tried to disable VT-x features from the settings menu-> System -> Acceleration. But curiously enough when I start the guest again, I get the same error and when I check the setting I see that Vt-x features have been re enabled automatically. Why does VT-x features get re enabled without my intervention and when I specifically disabled it ? This problem is only common to all 64bit guest OSs. I get no such problem when starting up a guest 32bit OS.
My main questions are -:

• What are VT-x features and what do they do ?
  Why even after I disable them from the settings menu do they get re enabled again when I start the guest OS ?
  How can I permanently disable/enable VT-x features so that I can start my 64bit guests without any problem ?
  This problem seems to be common to Windows 8 why is that ?

Thank You.

VT-x is hardware support for VMs, similar to high end graphics cards providing hardware support for 3D graphics. The VBox devteam decided that their 64bit guest support would rely on VT-x, hence you can't run 64bit guests without VT-x.

The above statement is true regardless of whether your host is 64bit or 32bit.

Some Win8 hosts have Hyper-v (a VT-x client) start at boot time, it runs the Win8 "host" as a VM. That is what prevents VirtualBox from accessing it.

mpack wrote:VT-x is hardware support for VMs, similar to high end graphics cards providing hardware support for 3D graphics. The VBox devteam decided that their 64bit guest support would rely on VT-x, hence you can't run 64bit guests without VT-x.

The above statement is true regardless of whether your host is 64bit or 32bit.

Some Win8 hosts have Hyper-v (a VT-x client) start at boot time, it runs the Win8 "host" as a VM. That is what prevents VirtualBox from accessing it.

• I have tried disabling Hyper-V and running a 64-bit OS but I still got the same error. Is there any way to solve this problem on Windows 8 or is VBox completely incompatible for Windows 8 ??
  What are the benefits of running your main OS as a VM ? Doesn't it make the performance of the OS slow ?
  Why can't VBox access hyper-V even if Windows 8 is running as a VM ? Is it because only one OS at a time can access the Hyper-V client ? Or are there are issues as well?

Hyper-V locks the VT-x extension completely, making it unavailable to other programs - simple as that.
Virtualbox is not incompatible with Windows 8 at all, but definitly not working if VT-x is locked by another process.

Thanks. I solved the problem. I just had to enable "Intel virtualization features" from my BIOS. Now VBox runs fine without any problems, but now I am getting a warning at the startup of the VM as "Warning HostAudioNotResponding" what can I do to resolve this problem ?

One question per topic please. And search before asking the question.