@echo off
setlocal
set BCDEDIT=%SYSTEM%\bcdedit.exe
if not exist %BCDEDIT% exit 1
for /f "tokens=3" %%A in ('%BCDEDIT% /create /d "PXE boot" /application bootsector') do set guid=%%A
%BCDEDIT% /set %guid% device partition=%SystemDrive%
%BCDEDIT% /set %guid% path \grldr.mbr

REM you can use /addfirst instead, if you want
%BCDEDIT% /displayorder %guid% /addlast

REM this sets a 5 second timeout until the default entry is booted
REM feel free to adjust to your needs, but NEVER set it to 0 or 1
REM in combination with using /default below unless you don't ever
REM intend to boot back into Windows again.
%BCDEDIT% /timeout 5

REM "bootsequence" means only the single, next reboot will default to this
%BCDEDIT% /bootsequence %guid% /addfirst

REM alternatively, you can uncomment this and make the ThinClient 
REM boot option the default boot option
REM %BCDEDIT% /default %guid%

endlocal