Transfering themes from my computer to the...

i can't seem to work out how to transfer the themes i've downloaded to the mobil, although I've installed and uninstalled then reinstlled the disk given with the phone i can't seem to connect to the phone through usb it always says usb not reconized and coud be faulty, but we've use the usb outlet heaps of time with no problems, could there be something eles wrong somewhere eles???. if th usb is not the problem what was the correct way to transfer the themes to the mobil help. lisa

nothing appers in my computer everytime i insert the usb of my mobile