To add to mciahel’s response:
It would also be helpful if you gave me the exact series of MyBook drive (Essential, Home, etc.). If you have the Essential, then you have a USB 2.0-only external drive and thus an eSATA-to-USB cable (if such a thing even exists) would not work (and even if it did, the drive would perform no faster than the USB connection by itself since the performance would then be limited by the USB controller in the drive enclosure). Plus, signal-wise and electrically eSATA and USB are not directly compatible with one another.
On the other hand, if you have the recently discontinued Home edition, you have an external hard drive kit which can use USB, FireWire 400 (IEEE 1394a) or eSATA connections. I have a 1.5TB version of the Home edition, and its sequential transfer speed is just about as speedy (via eSATA) as my system’s main internal 1TB WD Caviar Black hard drive (at about 90 MB/s, which is nearly 3 times faster than USB 2.0’s maximum practical throughput) although the external drive’s random access performance suffers a bit due to the fact that these externals were built for energy conservation first, performance second. Unfortunately, WD’s current external hard drive kits for Windows PCs are all USB 2.0-only and thus their maximum sequential throughput is limited to 30-ish MB/s. FireWire 800 (IEEE 1394b) and eSATA interface MyBooks are still manufactured, but only for Macs. WD has recently introduced a USB 3.0 version of its MyBook for Windows PCs equipped with USB 3.0 ports although the initial offerings in that series will be priced at nearly triple those of the current USB 2.0 models per TB. And then, one would need full USB 3.0 support in order to take full advantage of those drives’ performance; otherwise, when connected to a USB 2.0 port, they will become equally as handicapped as other current USB 2.0 external hard drive kits.
And as WD states in its instruction manual, the eSATA connection on its Home series of external drive kits is not hot-pluggable. Both the computer and the hard drive must be powered down before connecting or disconnecting the hard drive. Thus, even if you acquire a hot-plug capable eSATA card, the hard drive’s eSATA connection isn’t hot-plug capable at all.