The following solution below fixes the stop 0x0000007b usb boot problem for windows 7:

It basically enables usb drivers during boot process:

Save the text below starting from " to a file called set_7_usb_boot.cmd:

Then run it on the non-running windows installation to be fixed for usb boot problem:

set_7_usb_boot X:\windows

where X is the window installation to be fixed.

"

@echo off
setlocal EnableExtensions EnableDelayedExpansion
pushd %~dp0

rem set_7_usb_boot.cmd v0.02
rem created by cdob
echo prepare offline windows 7 registry, set USB boot drivers &echo.

set System_Root=\Windows
if not %1.==. set System_Root=%1

if not exist "%System_Root%\system32\config\system" set /P System_Root=Path to your SystemRoot folder on usb drive (e:\Windows):
if not exist "%System_Root%\system32\config\system" (echo Error: target not found &pause &popd &goto :eof)

copy "%System_Root%\system32\config\system" "%System_Root%\system32\config\system_%random%.sav "
reg.exe load HKLM\loaded_SYSTEM "%System_Root%\system32\config\system"

set ControlSetDefault=
call :setReg Default
call :setReg LastKnownGood

reg.exe unload HKLM\loaded_SYSTEM
popd

goto :eof

:setReg
set ControlSet=001
reg.exe query "HKLM\loaded_SYSTEM\Select" /v "%1" nul 2&1 && (
for /f "skip=2 tokens=3" %%a in ('reg.exe query "HKLM\loaded_SYSTEM\Select" /v "%1"') do set /a ControlSet=%%a
set ControlSet=000!ControlSet!
)
set ControlSetNNN=ControlSet%ControlSet:~-3%
if %ControlSetDefault%.==%ControlSetNNN%. goto :eof
echo. &echo ControlSet "%ControlSetNNN%" used.

set Services=HKLM\loaded_SYSTEM\%ControlSetNNN%\Servic es
set Control=HKLM\loaded_SYSTEM\%ControlSetNNN%\Control

rem http://msdn.microsoft.com/en-us/libr...ded.1001).aspx
rem Deploying Microsoft Hyper-V Server 2008 R2 on USB Flash Drive
rem http://technet.microsoft.com/en-us/l...8WS.10%29.aspx
reg.exe add %Control%\PnP /f /v PollBootPartitionTimeout /t REG_DWORD /d 30000
rem Loads VHD, SD, and USB boot drivers.
reg.exe add %Control% /f /v BootDriverFlags /t REG_DWORD /d 0x6

set ControlSetDefault=%ControlSetNNN%
goto :eof
"

Bye,
Skybuck.