I forgot to mention the original hard drive in my HP pavilion ze5270 is still alive: Hitachi 2.5" 40gb 4200rpm hdd. Still has the original contents.

It made the laptop horribly sluggish. After using it for an hour, I decided right there to replace it with the Hitachi 5400rpm hdd. The difference in responsiveness was like night and day; certainly a lot more than a mere 1200rpm difference would indicate.