I have 2 Dimension 4700s and one older 8200 - iPod as well as Sandisk mini cruzer flash drive give error message of usb device not recognized. Tried all usb ports in both 4700s. Both devices work fine in older Dimension 8200 (which only has usb 1.1). Both devices work on both 4700's if I use an external usb hub.... Weird thing is that occasionally the devices ARE recognized without the hub.(!!??) Apple tech supp had no ideas, didn't bother with Sandisk tech supp since flash drive works with hub. Any ideas? Already uninstalled all usb devices in device manager & let windows reinstall. No change. Been happening for a couple of months. Using hub consistently as workaround now & devices work, but would welcome a real solution.