higher speed hard drive

was talking to a salesman at compusa about putting a higher speed hard drive i my laptop. He said that if I put a 5400 or 7200 rpm drive into a laptop that currently has a 4200, the newer drive will still run at 4200 because of the bios. Is that correct or does the drive rotate at specified speeds regardless of bios setings?

A newer ide drive is generally backward compatable to the older bus. An older laptop that came with an ATA66 drive will still run an ATA100-133 drive for this reason. How else would you be able to replace a drive in any older laptop/desktop? You just for the most part run at ATA66 drive on a newer model that requires at least an ATA100. The salesman at Compusa was talking out of his left ear there. If anything the newer would run slower to match the 4,200rpm? It will run at the drive's normal rpm.

Wow that was a lot to say a 7200RPM drive will run at 7200RPM regardless of the BIOS.

hahah people who post dont exactly want the complete techincal mumbo, just give them simple answer.

Well they don't call it "adding a new larger faster hard drive" for nothing.