Click start control panel administration tools computer management device manager scroll through all of your devices If you see a yellow question or exclamation mark ? ! or a red X you will need to update the drivers for this device right click select update driver/reinstall driver if you can see your usb device but its not working scroll to Ports(Com&Ltd) right click to update driver If you computer came with a motherboard disk the drivers could be on it. Rather doing a driver hunt which can take hours http://download.cnet.com/slimdrivers-free/3000-18513_4-75279940.html Windows XP/Vista/7/8
it might take some time being a freeware driver solution Note: it will find all of your outdated drivers
This will automatically search for and find the correct driver you will have to update every driver individually once you update you might be asked whether you want to restart or make a system restore point.

Click no to both of these then continue updating each driver free then restart once all of the drivers have been updated.

Hope this helps.