XP and the Empeg through USB are (for now) not a good combination. Chances are you won't be able to get it to work until an update of the beta software is available.

Instead, focus on getting your ethernet to work. Connect with serial and enter a fixed IP adress in emplode. Then try to re-connect to your empeg.
Before I had my router I also wasn't able to connect to my Empeg using DHCP. Now it works like a charm.
Also keep in mind that if you connect directly to a NIC, you'll need a crossover cable.