Time and location: Present day U.S.
I googled: "how to destroy a computer" "how to destroy a laptop" "acid in household cleaners" "fry a computer"
I could probably do more research, but I think this community will have much more interesting ideas.
Thanks in advance.
ETA: Great answers...I'm looking forward to more of them.
Some additional info: While the protagonists want to destroy the laptop, I think they don't want to bring the authorities down upon them (as fun as it would be to blow up the laptop with, say, a homemade thermonuclear device). And they've got the antagonist incapacitated, but he's not a negligible threat. So it needs to be 1) quick 2) sure to destroy the data 3) won't bring the fire department or the neighbors.
ETA2: I have to say, some of the aggressive tactics you guys are suggesting make my protagonist with rage issues seem like practically a pacifist. But I would expect no less from this comm, and you're giving me great ideas.
ETA (2-28-11): Found this link today summarizing research done at UCSD on this topic.