Changing the hard drives in portable computers was originally easy, in many portables it did not even require tools (at least to remove the drive and it's carrier). Then a few came up missing at Airports and Conferences. Crooks were stealing them for the sensitive information tehy contained. After that, all manufacturers started making it nearly impossible to change them (except the MacBook). Best left to the pros.
A Conundrum Wrapped in an Enigma Bolted Together with 14 Million Tiny Freaking Screws