Harddrive Lag.

Hello,
My computer keeps lagging when I enter a program. The computer freezes for less then a second and the sound freezes too. While it freezes you can through the speakers hear a sort of metallic noise.
It comes and goes. It usually happens right after I've transported the computer, and then ends up stopping.
Could my harddrive be faulty after the transportation? If so would it need replacing, or would a reinstall of windows work?

OS:
Win 7 64-bit.

HDD:
SEAGATE Barracuda7200.12 750GB

Any help is appreciated.