The trademark is "Eee PC", so I assume the one with the hyphen is the best candidate to be the canonical tag. There are only three affected questions, so this one should be easy.
All glory to Joakim Elofsson for finding this one.
Going with eee-pc
There are at least some SuperUser users over the 500 rep mark, which would mean they'd be able to retag them into the same eee-pc box.