I have been pulling my hair out for the last week trying to figure out why the on board SATA to eSATA bracket and a PCIe eSATA card would not drive my Western Digital MyBook. I was playing with drivers, looking at bios corruption and reading through just about every opinion on what could be causing the problem. It turns out that the eSATA cable has too much material covering the connector and not allowing a good connection to the port in the unit. I had to trim up both ends of the cable so it can go further into the port and Wham! I am in business. Just putting it out there for anyone who may be experiencing the same problem. I really wanted the full speed of eSATA now that I have my mac pro. *sigh* all is right with the computer world again.