VirtualBox: using physical partition as virtual drive [duplicate]

What you are looking for is called "raw hard disk access" in VirtualBox.

Basically you create a virtual disk in vmdk format and configure it to direct to the desired partition or drive.

You can find a description in the manual under Advanced topics / Advanced storage configuration / Using a raw host hard disk from a guest

However keep in mind that, in the setup you are planning, the hardware that the operating systems see constantly changes. (your actual hardware when started as host OS, some virtualized hardware when started as a guest). Linux might cope with that but I am quite sure Windows will not handle that well. Also it might suspect you are using the same Windows licence on several computers and force you to reactivate often or flag itself as pirated.

Another issue might be how to tell the OS to use either the virtual drive (as guest) or the actual physical one (when started as host). Under Linux it might work to fiddle around so that both are assigned the same device name (like /dev/sdb1).