Use the Microsoft Tool: Disk2vhd: http://technet.microsoft.com/en-us/sysinternals/ee656415.aspx to convert you’re current Windows installation to a VHD.
Copy the created disk to you’re USB disk on E:\VHD
Open an elevated command prompt right click C:\Windows\System32\cmd.exe and click on “Run as administrator”
Type: bcdedit /copy {current} /d “New VHD Description”
This will return a GUID in my case {7dc00261-ee87-11de-8bd6-df41f0c5a8db} that must be used in the following statements:
bcdedit /set {7dc00261-ee87-11de-8bd6-df41f0c5a8db} device vhd=[E:]\VHD\newvhd.vhd
bcdedit /set {7dc00261-ee87-11de-8bd6-df41f0c5a8db} osdevice vhd=[E:]\VHD\newvhd.vhd
bcdedit /set {7dc00261-ee87-11de-8bd6-df41f0c5a8db} detecthal on
You can replace [E:]\VHD\newvhd.vhd with the path and name of your VHD.
After rebooting you should se the entry: “New VDH Description”
If you want to delete the entry enter:
bcdedit /delete {GUID} /cleanup