It is luck of the draw most often. There are bound to be a few defective drives when they are mass produced as they are. I currently have a 40GB maxtor and a 80GB WD 8MB cache running in this machine and they both work great without a hitch. The WD isn't all that old but the Maxtor's been going at it for quite some time now. Whichever drive you pick just get one with a 3 year warranty and you should be set.