USB Port does not recognize device

This is the situation. Bought Compaq V5000 used. USB port does not recognize device msg pops up when device is pluged in. I have paid $100 to computer techs at shops that cannot fix problem. Last owner said a new motherboard was installed. Device manager says port is working. USB ports have been uninstalled, re-installed, Chipset has also been uninstalled and reinstalled. There is power because it charged a digital picture frame for a key chain. Please help. Getting ready to throw this piece of &*^% in the trash.