1. What are you using for a cable to go to the GPS? You either need an Aero to GPS cable or if you use the Aero's PC Cable, you'll need a "null modem/gender changer". I've seen a lot of people get straight through gender changers, and this won't work. 2. Try resetting the Aero. You can do this by inserting your stylus into the reset button in the back of the Aero. This will not erase the unit, but will reset it and make sure nothing is running in memory (kind of like rebooting a PC). 3. On your Aero go to the "Start" menu and select "Settings". Go to the "Connections" tab and select "PC". Turn off the option to "Automatically synchronize when serial cable is connected". I've seen a couple cases where the Aero keeps trying to connect to the desktop and it then can't see the GPS. If you do this, you'll need to turn the option on again when you synchronize with the desktop. 4. Run Site Mate and go to the "Configure" tab. Go to the "Settings" area and select "GPS Settings". Verify that the Com port is set to 1 and the Baud Rate and other settings match your GPS receiver. 5. Finally, with the GPS receiver hooked up, take a look at the bottom of the screen of Site Mate. What error message is showing up? Let me know as this makes a difference in the type of problem you may be having.