I have an early 2009 Mini, with 5 USB2 ports. One is connected to a 1TB HDD for Time Machine back-ups. It works fine, as did the 320 GB one it replaced. The others are used for a mobile broadband dongle (neither a telephone line nor wifi available to my apartment), the Apple keyboard with the mouse connected to that, and a printer. The fifth is used occasionally, directly, or through a powered hub. Thumb-drives (USB sticks / call them what you like) work fine using the keyboard USB2 port. HDD USB2 drives are not even recognised. I have tried plugging into the spare port on the keyboard, using the spare port on the Mini through a powered hub and directly, and also using the port I use for the printer (though a hub) .. all to no avail. I have tried using my retired 320 GB HDD I wanted to wipe it and put it to another use. I tried using an 80 GB HDD loaded with a couple of movies and some rugby games, given to me to watch by a friend. Can anyone help a none too tech smart old chappie, without a youthful Apple savvy geek to hand?