Hmm, i'd suggest no, it wouldn't be as easy.
Its probably possible to do, but the parts won't be very cheap anyway.
Laptops are basically miniture PC's and so use different parts, i.e, smaller ones and these are expensive.
I guess it is possible to build one, though, but you'd need to make sure you got supportive parts, and laptop ones I would think would work slightly differently than PC parts in the way they connect up to save space, etc.
Good luck with it