Western Digital alleviate the storage bottleneck with the 150GB WD1500AFHD RaptorX, a serial ATA hard drive with a clear window into its inner workings. Western Digital offers two variants of its high performance 150GB HDD, the Raptor WD1500ADFD and the RaptorX WD1500AHFD. The difference between the two is that Raptor 'ADFD' has a solid steel top while the RaptorX 'AHFD' has a crystal clear plastic see through top - so you can see the hard drive platters spinning and the read arm moving rapidly back and forth. The Western Digital RaptorX is the only hard drive on the planet that lets you look into the heart of the drive.