Let me start with a warning. External drives are far less reliable than internal drives. If you want to use it for storage, be sure to have a good backup of everything you put on it and don't want to lose. A second and third hard disk are fine, burning to DVD is fine, webbased storage is fine. Having no backup is a potential disaster.
An external hard drive always connects via a USB2-cable (or Firewire if you have a Mac). It can be USB-powered (which uses some power from the laptop, indeed) or externally powered (power adaptor). That doesn't make a difference for the performance.
Kees
I have a new Dell Studio and want an external hard drive for added storage and to prevent slow down. What are the disadvantages of the portable unit? Is the battery running down a problem?
It would be nice to have a portable so you didn't have to deal with a cord all the time, but I'm just not sure about how a portable compares in performance to a regular external HD.
Also, could you recommend a particular model with at least 500GB or preferably a little more?

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