This is a 3.5" drive. You must have a 2.5" laptop drive. The 2.5" enterprise drives may sometimes be mistaken as a laptop drive due to form factor, but clearly it isn't. They are tall drives as well (around 15mm).
The Velociraptor is now 2.5" form factor because the smaller the platters, the faster the access time. They still need a 3.5" drive bay because they have a heatsink that makes them into a 3.5 drive.