Is it possible that apache does not have access to Z:?

Most likely. Services usually run as "Local System", and even if not, they run in different sessions than normal users. Since about Windows XP / Server 2003, drive letters are no longer global, but per user (or session, dunno). Microsoft recommends using UNC paths (i.e. \\server\share\some\path instead of x:\some\path), another way that still works (but who knows for how long?) is to install and use the AutoExNT tool. This tool installs as a service and runs a batch file whenever its service is started. From that batch file, one can map drive letters using net use x: \\server\share /user:foo topsecretpassword.

Alexander