Had the same problem, bought a new Dell laptop and to my horror when I came to look for the serial port it didn't have one, at first I thought I was in trouble but then was given a USB to serial connector by a computer bod, it work a treat and have had no problems at all, but you will have to find out which port number is relates to, on mine it is coms port 4.
Link to the one I am using.
http://www.mutek.co.uk/acatalog/USB_...onverters.html