Make sure you are using the right kind of cable.

Make sure your computer's BIOS is set up correctly so that the COM port is activated.

Make sure Windows can see the COM port in Device Manager.

Make sure you're not running any programs such as Palm Sync which grab the com port.

More details here. Try to connect with hyperterminal first and see if that works. If you can't get that to work, then the upgrader won't work either.