Batch file 'choice' command's errorlevel returns 0

I'm trying to create a batch file that performs different 'choice' command based on the version of Windows being executed on. The choice command's syntax is different between Windows 7 and Windows XP.

Choice command returns a 1 for Y and 2 for N. The following command returns the correct error level:

Windows 7:

choice /t 5 /d Y /m "Do you want to automatically shutdown the computer afterwards "
echo %errorlevel%
if '%errorlevel%'=='1' set Shutdown=T
if '%errorlevel%'=='2' set Shutdown=F

Windows XP:

choice /t:Y,5 "Do you want to automatically shutdown the computer afterwards "
echo %ERRORLEVEL%
if '%ERRORLEVEL%'=='1' set Shutdown=T
if '%ERRORLEVEL%'=='2' set Shutdown=F

However, when it is combined with a command to detect the Windows OS version, errorlevel returns 0 before AN after the choice command in both my Windows XP and Windows 7 blocks of code.

REM Windows XP
ver | findstr /i "5\.1\." > nul
if '%errorlevel%'=='0' (
set errorlevel=''
echo %errorlevel%
choice /t:Y,5 "Do you want to automatically shutdown the computer afterwards "
echo %ERRORLEVEL%
if '%ERRORLEVEL%'=='1' set Shutdown=T
if '%ERRORLEVEL%'=='2' set Shutdown=F
echo.
)

REM Windows 7
ver | findstr /i "6\.1\." > nul
if '%errorlevel%'=='0' (
set errorlevel=''
echo %errorlevel%
choice /t 5 /d Y /m "Do you want to automatically shutdown the computer afterwards "
echo %errorlevel%
if '%errorlevel%'=='1' set Shutdown=T
if '%errorlevel%'=='2' set Shutdown=F
echo.
)

As you can see, I even tried clearing the errorlevel var before executing the choice command, but errorlevel remains at 0 after the choice command is executed.

Any tips? Thanks!