Samsung is an alternative choice to WD & Seagate... they seem to be quieter, and just as reliable, also prices are about the same.
I like WD too, I have a IDE 120gb 5400rpm hdd thats 5 years old and has gotten alot louder, it whines like a raptor now which is annoying. The hdd will click sometimes, especially after days of not using it, but will stop after a few hours, which is a reason I chose the Samsung.
C2D E6600 @ 3.15ghz w/ 1.35 vcore
2GB G.Skill DDR2-800 (4-4-4-12)
XFX 7600GT xXx