If you do want USB to Serial then this one works fine for me running W7 http://cgi.ebay.co.uk/USB-2-0-RS232-Serial-DB9-9-Pin-Male-Adapter-Cable-PC-/250653067355?pt=UK_Computing_CablesConnectors_RL&h ash=item3a5c16485b
I use a Netbook for mapping (much less bulky than a full size laptop) and it doesnt have a PCMCIA slot.