Hello. I have a brand new, 15' macbook pro. I have noticed that the computer only has two USB hubs, but I need to plug in multiple peripherals, such as a mouse, flashdrive, printer, external hard drive, etc. I recently bought an unpowered four-port USB hub. I am guessing that the power to the USB ports is limited, and so I should only run devices with low power requirements off of it. What are the power requirements of various USB devices? I know this seems like a simple question, but I cannot find a list on the internet. For example, the external hard drive and printer both have their own power supplies, so am I to assume that these are low power devices? Are flash drives low power? What about optical mice? Any help is greatly appreciated. Thanks.