Plug in a usb 2.0 flash drive and see what Windows Xp says. I have a usb 1.1 bus speed on one of my machines and every time I plug in my usb 2.0 corsair mem card, XP says "this drive will preform faster in a highspeed usb hub" in a pop-up bubble. If this bubble doesn't show, you most likely have usb 2.0.