You installed a driver with the USB-serial adaptor, right? Right click "My computer", select properties and go to device manager. Look at the COM ports. Your USB-serial adaptor ought to show up there and you should be able to see what com port it is on. (Sorry, rereading your post it looks like you may have done that but I'm not sure so I'll leave the instructions in).
Beyond that, XBrady's earlier version of GPSsecure had a little window that you could see the NMEA strings streaming by and it shows the satellite locks. Maybe PM him for a version 1.0 of it.