If you take a computer designed for 120V AC to Europe, chances are its power
adapter will be dual-voltage: get a simple plug adapter, and you can just plug
it into a 240V outlet.

But there can be weird side effects:
- I once had a laptop that felt sort of weirdly charged (the hair on my hands
  would stand on end when I touched it, and sometimes I felt a faint continuous
  electrical shock through my wrists when they rested on the laptop body).
- My 2nd generation ipod nano feels "buzzy" if you run your fingers over it
  when it's plugged into my netbook, when the netbook is plugged into the wall
  on a 240V circuit. Disconnecting the netbook from the wall makes the buzzy
  feeling go away.
- If I firmly grip the ipod with one hand and stroke it with the other, it does
  not feel buzzy (presumably because it's grounded to me).
- My kindle paperwhite's touchscreen goes haywire in the same setup -- it
  behaves as if I'm doing all kinds of crazy multi-touches.
- I can solve the Kindle problem by plugging my ipod charging cable into
  another USB port on the netbook, and pinching the exposed metal part with my
  fingers -- if I then touch the Kindle with my other hand, it behaves