I recently learned about the usefulness of batch files when finding a means of performing a silent setup. To ensure that the batch file would work on any system I used one of the default windows environment variables. These variables are helpful to reference the path to a given file in a windows environment. This allows you to substitute the environment variable with the path in the command line and ensure that it will work even if the given system has different drive letters or directory structure.
A useful reference for understanding environment variables together with a list of Windows predifined variables can be found at: http://vlaurie.com/computers2/Articles/environment.htm