If anyone is interested, the Targus CF Serial I/O card works very well on an Axim X5 Basic running WM2003 with a Magellan GPS 310 and Pocket Streets 2004. The card shows up as COM5. I assume this card will work with any GPS that has a standard serial connection. No null modem adpater, gender changer or custom wiring was required for the Magellan GPS 310. I just plugged the Magellan PC 9-pin data cable into the card's cable and it worked.
The Targus CF Serial I/O card has been discontinued but the drivers from Socket Communications work great on WM2003.
http://www.socketcom.com
The cards can be purchased here:
http://www.compgeeks.com/details.asp?invtid=PA611U
Use coupon code TECHBARGAINS for 10% off the regular price of $29.
Your mileage may vary. ;)