@echo off
cls
SET THIS_VARIABLE_IS=EXACTLY
IF NOT '%THIS_VARIABLE_IS%'=='EXACTLY' GOTO ERROR
goto env_ok
:ERROR
echo This computer does not have sufficient DOS environment space free for
echo the Walkthroughs & Flybys CD menu system to operate. Please allocate
echo at least 25 additional bytes of environment space. The easiest way to do 
echo this is by adding the following line to your CONFIG.SYS file and then
echo rebooting.
echo:
echo    SHELL = C:\COMMAND.COM /E:### /p
echo:
echo For DOS 3.1 replace ### with the number of 16-byte blocks you require.
echo For 3.2 and up, replace ### with the actual number of bytes.
goto end
:env_ok
SET THIS_VARIABLE_IS=