Detect USB inside a WinPE session

1) Open CMD or Command Prompt window.
2) Type Diskpart
3) At DISKPART> prompt comes out type automount
you will get a message saying "Automatic mounting of new volumes enabled."
4) Type Exit, to get out of diskpart.
5) Plug in usb hard disk or Thumbdrive

diskpart and imagex sample

disk.txt

select disk 0

clean

create partition primary size=300

format quick fs=ntfs label="Boot"

assign letter="S"

active

create partition primary size=61440

format quick fs=ntfs label="System"

assign letter="T"

create partition primary

format quick fs=ntfs label="Data"

assign letter="U"

Exit

--- image calls

diskpart /s g:\disk.txt

net use f: \\svr\Image2011$

x:\gimagex\install\x64\imagex /apply F:\Systempart.wim 1 T:\ /verify

x:\gimagex\install\x64\imagex /apply F:\Datapart.wim 1 U:\ /verify

T:\Windows\System32\Bcdboot T:\windows /s S: