With 500 GB of storage, this is a good HDD drive if you need a larger storage unit. This model's rotation speed is 10 000 rpm.
From eBay
Western digital velociraptor 500gb 2.5" 10k rpm sata 6gb/s hdd wd5000bhtz
Softhands
Western Digital 500GB VelociRaptor WD5000HHTZ SATA III