It used to be that any electronic item crossing the border aroused suspicion. But that was more common when Canadians had a smaller personal exemption, duty was charged on just about everything, and items like computers and cameras were
really expensive. That was then, this is now
Laptops are now so common that they would not be suspected of being a new purchase unless they were brand spankin' shiny new, still in a box

Like cell phones, just part of our day to day lives now. I know I never go on vacation without one. Mine is older, but it has wireless capability and most hotels offer free highspeed, so it's very handy to have with us.
Also, laptop prices are pretty low in the states now so if you were away for a week, a laptop would likely fall within your exemption anyway. And if it were American made, there's no duty -- so even if it didn't fit into any exemption you had AND it
was new, you'd only be paying the tax
Another thing to keep in mind ... personal files like photos and emails on the laptop make it pretty easy to show that you've had it for a while
