Re: Switching from Win 8 DP in Virtual Box to installing in separate partition
First to address the problem that is making you want to perform this task, see my comment to your thread here which should work and maybe make this thread moot.
Now to this issue.... As a VirtualBox VM is created using generic, virtual hardware which is by its' very nature and definition "Virtual" and does not actually exist on the host machine I can't really imagine how or even if the VM would function as a real OS boot option on a second partition in some sort of dual boot scenario, but.... depending on the type of VM Disk you created (usually .vdi by default), if you actually used the .vhd option you may want to take a look at this article about using Virtual Hard Drives as boot options and see if something like that might work for you.
Regards
Randy

It is never my intent to sound abrupt or discourteous. Often I am just being as quick and succinct as possible, since I assume getting a fast response to your issues is as important to you as seeing your issue resolved is to me. I apologize in advance for any unintended hurt. Best regards Randy.
OS Service Pack Windows 8 Consumer Preview 64bit
Internet Explorer Version 9
DirectX Version 11
Computer Type Home Built
CPU Type and Speed AMD Penom II x6 3.2Ghz
CPU Cooling Factory
CPU Idle Temp 30 C
CPU Load Temp 47 C
Motherboard Chipset Gigabyte GA-870A-UD3 AM3 AMD 870
System BIOS Revision Award v6.00PG
System Memory Type 16 gigs Gskill Ripjaws
System Memory Speed 1333
System Memory Clocking 9 9 9 24
Video Card Type and Speed Nvidia 450 GTS 1Gig DDR5
Video Card Cooling stock
Power Supply Unit (PSU) Antec EarthWatts EA750 750W
Computer Monitor Dual 23" Dell LCDx
Sound Card Realtek High Definition Audio
Speakers Klipsch
Headset/Microphone Altec Lansing
Network Speed Comcast Cable, usually around 16 Meg
USB Controller Renesas Electronics USB 3.0 Host Controller
Gaming Console Xbox 360
Anti-virus Software Microsoft Security Essentials
Productivity Suite Microsoft Office 2010