Accessing USB drive form WinPE prompt - windows-8

Question

I am trying to install Windows 8 on virtual box using a bootable WinPE DVD. The image file (.wim) is on the USB stick.
But when I boot from DVD, I cannot find the USB drive.
I need to execute the command
d:\imagex.exe /apply e:\imageC_20150528.wim 1 c:\
where D - dvd drive and say E - usb drive
But I cannot locate the USB drive from the command prompt.

Answer 1

When I use winPE I use DiskPart to determine the drive letter of the USB drive.
-Diskpart
-list volume
This should display all available drives

Answer 2

If the USB drive was inserted before you booted the system into PE, then the USB drive should already be mounted and have a drive letter. If it doesn't then it is likely the drive isn't supported (you might want to change your boot-image/disk to include additional drivers/tools to get access to your usb controller and connected device).
If your USB drive was inserted after you booted the system into PE (and your hardware is supported in PE) then I usually can access the disk in the following manner (worked even in XP PE):
go to commandline and start diskpart (following commands are in diskpart):
issue command: rescan enter
This 'Locates new disks that might have been added to the computer.'
Depending on diskpart version (and/or it's automount setting) this can be enough to automatically mount the file system for a new basic volume when it adds the drive to the system and assigns a drive letter to the volume.
When it doesn't, follow the following 2 steps:
command: list disk enter
to see a list of disks and some info (to check the drive was found)
command: list volume enter
lists volumes on all disks (to find volume number of the USB drive)
command: select volume=# enter (where #= volume number)
to select the specified volume and shift the focus to it
command: assign enter
to assign the next free letter to the current focused volume
OR: assign letter=# enter (where #= driveletter of choice)
This method usually works for me on most hardware.
See also: Diskpart commandline options on MS Technet

Answer 3

Really - you should be using a fairly current version of winPE - 5.1 is what I'm using - which is the version that parallels windows 8.1. I'm switching over to winPE 10 (they changed the numbering to be consistent with Windows)
The reason I bring this us is because you're using imagex - and dism.exe has largely replaced imagex.exe in more current versions of winPE.
If you're just doing this at the command prompt in a generic winPE, you can use mountvol.exe (with no parameters) to discover the drive letters that are available. Everything shifts around drive-letter-wise when you're in winPE. So it might not be e: any more.
Also, dism and/or imagex would be on the x: drive - which is the virtual drive that the winPE creates when it boots.