iTunes does not recognize iPod Touch.

I just got a iPod touch 3 days ago and it wouldn't show up in iTunes. I made sure I had the newest version of iTunes, tried other iPods on my computer (iPod with click wheel and 80 gig iPod Video), and called apple care and followed the steps they walked me through. They told me it must be an issue with the iPod Touch itself so I returned it to Best Buy and got another one. This one is doing the same thing and I don't know what the problem could be. Any help would be appreciated.