I agree with Larry. Back up your valuable data files - the drive might still be under warranty although I'm not sure if you'd really want a replacement with the same unit.
We have hundreds of Gateway computers at work which have the same Quantum hard drive model as yours. Mine started acting up a few weeks ago by making occasional loud clanging noises. Finally it crashed and was replaced.
Our data systems technician told me that they've experienced many problems with these Quantum hard drives with the first symptom being the loud noises.