Hi Orianel,
Make sure you have the proper drivers installed in order to get sound routed through your interface.
archive.digidesign.com/download/audiodrivers/xp/
Any audio routed with your Pro Tools drivers will need to go through your interface. Have this selected as your playback device within the Control Panel under the sound settings and make sure you have a pair of speakers or headphones connected to the interface. A restart may be required but you should be all set after this.
Sincerely,
Rob Fusco
Berkleemusic
Customer Service Rep