Question: I have to run Mac OS on virtual box for a class and it keeps giving me errors stating 

"VT-x/AMD-V hardware acceleration not available on your system. Certain guests (e.g. OS/2 and QNX) require this feature and will fail to boot without it."

If there is a solution, I am not used to windows 8.1 and will need detailed instructions on how to fix it. Thank you

Answer: 
***You don't have to uninstall/reinstall HyperV***

I ran into this same issue using the new Visual Studio 2015 Android emulator and Windows Phone emulator, while also trying to run VirtualBox clients. Unfortunately you can't run VBox at the same time as the other emulators; you just have to setup a new boot option and reboot to switch back and forth.

Open an administrative command prompt and run:

```
C:\>bcdedit /copy {current} /d "Windows w/ HyperV"
C:\>bcdedit /set hypervisorlaunchtype off

```

This will copy your current boot settings to a new boot option called "Windows w/ HyperV" and then will disable HyperV under your current boot option. You can run "bcdedit" with no parameters to check that {current} has the hypvervisorlaunchtype set to "off" and that the new section has hypvervisorlaunchtype set to "auto"

See [Scott Hanselman's article](http://www.hanselman.com/blog/SwitchEasilyBetweenVirtualBoxAndHyperVWithABCDEditBootEntryInWindows81.aspx) for more information.
As previous replies have said, check if your processor supports VT-x virtualization. If it doesn't, then you just won't be able to run Mac OS on VirtualBox. If that is the case, consider VMWare Player, which is a decent alternative for VirtualBox, and is also free. It is commonly used in computers whose processors don't support VT-x to emulate Mac OS.