also need to add, that laptop motherboards are unique to each design case, so you wont likely be able to find one that fits the basically empty clamshell your looking for.
http://www.ewiz.com/system_notebook.php?code=Barebone lists an MSI barebone having a 15.4 inch screen (with motherboard) for $571 so I would hope that, without the motherboard, it should be possible to source the case, screen, psu etc for considerably less.
MichiganTeddyBear:
The motherboard which I have in mind is considerably smaller than 'normal', so I guess that there should be enough space for it
Overall, it's not worth building a laptop. For $889, you can get this. Again, you don't save money by building a laptop considering the CPU in that Toshiba is $207.