Why won't iTunes recognize my iPod, but my brother's iPhone?

My iPod 4 isn't being recognized on my Windows computer (I know,i should REALLY get a Mac instead, but I have no money at all...), but the computer recognizes my brother's iPhone 3g (NO s). But, my Ipod is recognized on my dad's computer, but not mine, I use Windows 7 Professional, and my dad has Windows 7 Ultimate. I tried reseting and restarting Apple Mobile support on my computer in settings, but it still won't work. I've plugged in my iPod in every USB port in my cimputer, but it still won't recognize. I have the most updated iTunes, I've uninstalling iTunes and installing it again, but it STILL won't recognize. PLEASE HELP!