access to local disk – business server 2003

Hello

Our company takes care of a network in another company with approx. 50 workstations… Recently they have decided to install an application on every workstation that needs to write files on local disk (which cannot be done because users don’t have that permission)…

so the question is: how can i change users permissions so the can have “write” permission to whole local disk.

Please try to explain it as simple as possible, I’m new to this server things :)))