Perhaps, the device is being used by another program since SiRFDemo comes back with that error message. Apparently, you can't use two programs at the same time. You would have to close the other program first before using the device with another program.
First, to make sure you have the latest drivers installed, please follow the instructions below:
Please unplug the BU-353S4 and 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/62/windows_pl2303_usb_driver.zip
). Make sure to extract the file and install the exe file.
Plug in the device 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). Take note of that com port.
Install this program: (http://www.usglobalsat.com/store/downloads/GPSInfo.zip
). Open it up and extract it. Bring your computer outside where there is clear access to the sky and no tall buildings or trees.
Click on the GPSInfo program, select the correct com port, and choose the appropriate baud rate. Press 'Start GPS'. You should see some scrolling data below. Also, check if the red light is blinking.
Let me know how it goes.