The part number (from Intel) for the only 500-supported modem pc card is CM-56G:
http://www.intel.com/network/connectivity/emea/eng/products/xircm56g.htm
There are some combo cards (10/100 Ethernet + modem) with similar names (i.e. Xircom CreditCard xxxxxxx), and they are NOT supported by WallBotz500.