First, did you download the drivers from the website from the CD or from the USG Website? Also, have you tried plugging in the device to a different USB port?
Uninstall the driver. You can do this by going to Control Panel > Programs > Uninstall a program > select PL 2303 USB-to-Serial. Turn off your computer and wait for a few minutes. Power up your computer and download this driver: (http://www.usglobalsat.com/store/download/590/windows_allinone_usb_driver_v130.zip
). Make sure to extract the file and install the exe file.
Plug in the device with the provided extension cable and check the Device Manager. You can do this by right-clicking on Computer > Manage > Computer Management > System Tools > Device Manager > Ports (COM & LPT) > Prolific to USB Serial Comm Port (COMXX).
Now, test the device with the ND-100S Test GPS Utility. It is a testing utility for most of our GPS Receivers. Click on the link for download: (http://www.usglobalsat.com/store/download/590/nd-100_gps_test_setup.zip
). Extract the file and install the program. Open up the software, select the correct com port, choose the appropriate baud rate, and press 'Connect'. In the Terminal tab, you should be able to see the scrolling data coming from the device.
Also, bring your computer outside where there is clear access to the sky and there are no tall buildings or trees around the area. Check if the blue light on the device is blinking.
Let me know how it goes.