Universal Paths (Please Help)

I've created 2 discs with WPI. One Disc is Windows Unattended Installation which installs Windows XP and some basic things, after that copies the folder WPI to the systemdrive and when I finished the installation I'm running WPI and continue the installation of the other applications. In This Case I'm using the variable %systemdrive% in the WPI Configuration File.

The Second Disc is an Application Installation Disc, I have the same applications and in WPI Configuration file I use the variable %cdrom% so I'm doing the installations direct from the DVD disc.

My problem is that I have to maintain 2 different configuration files in WPI. I thought that I would use a universal path in config file "\\WPI\\Install\\Apps..." so it will no mater if the WPI is running from "cdrom" or "systemdrive" but with no luck, the WPI doesn't recognize this path.

Please Help me find a way to solve this

Thank you all.