yea it probably wouldn't fit.
I'm still curious to know if anyone tried it though..
apparently (from what I've read) you can't even upgrade the 6800 to the 7800
but then in other places they say it's fine to upgrade and that the m170 was specifically designed to allow you to upgrade the card.
It seems with laptops a lot of people just assume that the graphics cards can't be upgraded and it makes it hard to ascertain what's the real case.
anyways, if anyone has managed to upgrade the gpu in an m170 to a 8 series nvidia card or another shader model 4.0 card please do tell and give details on how you got it working ;)