Point of reference: An SL500 (2746-22U) that I'm typing on weighs in at 6 lbs 6 ounces on my digital scale, or 6.375lbs; slightly
more than the 6.3lbs specification that's in the SLBOOK.PDF. Of course that could be because the 160GB hard drive is about 1/3 full
. Or maybe because there's a T9400 (2.53Ghz) processor in here instead of the P8400 (2.26Ghz) that's supposed to be "stock", but it's close enough to the published specs. Are you taking into account the weight difference between the Z61t with a black vs. silver lid? The TWBOOK.PDF says that the black lid is exactly .25lbs lighter than the silver. There doesn't seem to be a weight spec for the 4 and 7 cell batteries so I can't tell the difference between them.