Xandros is probably using the cups print system. Open a browser, and in the URL, enter http://localhost:631
to get into the cups admin system.
Click on Manage printers. Do you see a printer listed?
If no, click on 'add printer' to add a printer (even though you have installed drivers, you still have to configure it).
If yes, click on 'manage printer' to go through the steps of configuration to see if it has an enable/disable setting that needs to be set to enable.