Error :
After connecting the GPS unit to a serial port adaptor, you might get an error message saying the com port is being used by another device or it is busy.

Cause:
Com port's baud rate probably isn't set correctly. This especially occurs on laptops.

Solution or Workaround:
Right-click on "My Computer" and click on "Properties"
Click on "Hardware"
Click on "Device Manager"
Scroll down and click on "Ports" (Com & LPD)
Double click on it and highlight the "usb serial adaptor" or something close to it.
Select "Properties" and click on "Ports Settings"
Set Baud rate to 4800.
Click on Apply and it should now work.