suunto dive manager & usb

Hi all,
Can anyone help me with the following problem, I have just purchased a sony
vaio laptop which has no serial port, before i bought the laptop i checked
on the net and found various posts telling me that the suunto computer
interface could be connected to a non serial ported laptop with the use of a
usb to serial adapter cable, i have now also purchased via ebay the usn to
serial adapter cable and installed it and the driver it was supplied with i
can find the adapter in device manager and it has been assigned com port 1
however i cannot get the dive manager software to find the pc interface
anyone any ideas or solutions ??
Regards
Mark