13 of 17Image
Under the System/Acceleration tab make certain that both Enable VT-X and AMD-V and Enable Nested Paging are checked.
Windows 8 wants all the graphics power you can give it. To do this, first enable both 3D and 2D video acceleration. This, in turn, will let you give Windows 8 up to 256MBs of video RAM, instead of the default maximum of 128MBs. Go ahead and up your video memory to 256. You'll be glad you did.
Next, move down to storage and go to your virtual hard drive (.vdi) under the SATA controller and click host I/O cache. While there, your Windows 8 Preview .ISO file should have been mounted already/ If it hasn't been yet , mount with IDE and make sure you're using IDE with the ICH6 IDE controller.