Enable AAM on Western Digital Hard Drive

A thread at Hexus here, describes another user's identical problem, and several possible solutions. The final "stop-gap" solution that worked for that user was using the Windows version of hdparm and setting up a batch file to run at startup, since the settings got erased at restart.

Many newer drives come locked into performance mode. I would recommend downloading the toolset for that particular drive and see if they provide a tool to make changes to the default drive settings.