Newegg has the Western Digital Caviar Blue WD3200AAKX 320GB 7200RPM 16MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive for $65 - $10 off with coupon code EMCYTZT1980 [Exp 8/1] = $55 with free shipping. Ultra cool and quiet drive features NoTouch ramp load technology, IntelliSeek, ShockGuard, and a 2 year warranty.
A 320 is a little bit dated in today's market. Even at $55.00
Couple of years ago you could pickup a wd black 640gb 32gb for $40 np. These should be $25.