The 120GB HDD on my MacBook seems a bit small to me. I found a 320GB HDD on CanadaRAM.com for $158. Specs are: 320Gb Samsung 320GB mobile hard drive 5400RPM 8 Mb cache 5400 RPM SATA Internal HD HM320JI My only question is, what about the free fall sensor on the MacBook? Is that a feature of the HDD, or of the laptop itself? Should I be looking for a HDD with a freefall sensor, or just go with this 320GB?