OK, how is this for a WAG ...

You have a usb keyboard and/or mouse attached to desktop.
Win 7 is detecting that ( or you have legacy support enabled in bios and it is detecting that ) and it is loading the usb 1 drivers. Since the laptop does not have them, it loads the usb 2 drivers.

Check the USB host controllers in the Device Manager.
Any that have Universal Host Controllers are USB 1
Any that have Enhanced Host Controllers are USB 2