The hard drive has a 5 volt power...often used to power a CPU fan.
You'll have to be somewhat careful if your putting that many USB devices on the IO. Draining additional power (above what USB normally provides) can cause the unit (or any computer) to shutdown. For what it's worth, I'd be inclined to get a RS converter for the USB hub. Again, it just depends on what devices your hooking up...how much power each device requires...etc.
Sorry, but I don't know if there's a better answer.