This is how I installed Windows 8 Developer Preview with developer package (64-bit) on Virtual Box which is on my 64-bit Windows 7 machine:
- Download some ISO mount tool.
- Download the windows 8 ISO. http://msdn.microsoft.com/en-us/windows/apps/br229516
- Download Virtualbox.
- Setup a new machine in Virtualbox, I gave mine 1.5Gb RAM and 20GB space. Windows 8 requires 1Gb RAM and 13Gb storage, so make sure you're over that.
- Set your OS as Windows 7 64-bit.
- There are some settings that is required for this to work. In the settings, go to System > Motherboard and enable IO APIC extended settings, then move to the Processor tab enable PAE/NX, then move to the Acceleration tab and enable the 2 hardware acceleration (Nested Paging and VT-x/AMD-V). (Most important part, why I even wrote this post).
- Start the machine, select the mounted drive and everything is common sense from there to install the OS.
Here is the machine setup: