[command-line] change directory in batch file using variable

Here's the question:

set Pathname = C:\Program Files
cd %Pathname%
pause

The above doesn't change the directory, as I would expect. Can anybody please tell me why?

simple way to do this... here are the example

cd program files
cd poweriso
piso mount D:\<Filename.iso> <Virtual Drive>
Pause

this will mount the ISO image to the specific drive...use