Using <a href=http://www.bigbold.com/snippets/posts/show/553>this silliness</a>, here's an example of BAT file that will lower-case a string given as an argument.
echo>%1 dir /b/l %1>lower.tmp set /p result=<lower.tmp echo %result%
Saving this as lower.bat, I run
lower "HELLO WORLD"
and get hello world as a result