The Western Digital MyBook Premium Edition external hard drive is physically portable but still humongous in terms of capacity. The 500GB unit we tested offered the most mixed performance of any external hard drive we've tested. Though we love its design, capacity, and small size, we were a little disappointed with its overall performance. Direct competitors in this space include the Maxtor OneTouch III Basic (500GB), the Seagate Pushbutton Backup Drive (400GB), and the Iomega External Hard Drive (400GB). All these drives cost about the same, though the Iomega also offers FireWire 800 connections. All have backup software, as well. The Seagate drive was a slow performer, while the Iomega was speedy when transferring over FireWire but slow over USB 2.0.

Drive type: external hard disk drive
Available capacities: 160GB; 250GB; 320GB; 400GB; 500GB--all drives have a 7,200rpm hard disk drive
Capacity of test unit: 500GB
Cache: 16MB for the 400GB and 500GB drives; 8MB for the rest
Dimension: 6.8 x 5.6 x 2.2 (HLD in inches); 2.6 pounds
Notable design features: backup button; book-like design
Connection options: FireWire 400, USB 2.0
OSs supported: Windows 98 SE/Me/2000/XP or, Mac OS X 10.2.8+
Software included: EMC Retrospect Express Backup and System Recovery Software (on drive)
Additional features: capacity gauge: the backup button features an LED that indicates how much space is available on your drive; the drive turns itself off when not in use
Service/support: one-year warranty; toll-free phone support: 9 a.m. to 7 p.m. from Monday through Thursday, 9 a.m. to 7 p.m. on Friday, and 8 a.m. to 5 p.m. CT on Saturday; e-mail support via an online form; Web site has a searchable knowledge base, FAQs, downloadable drivers, and software.

On CNET Labs' test bench, the 500GB MyBook was very sluggish when writing, via both FireWire 400 and USB 2.0 connections. The drive took almost 36 minutes to write our 10GB test folder, about three times slower than other hard drives with the same specs. On the other hand, in the read test, the MyBook drive took slightly less than 10 minutes to get the job done, which was the fastest among all of the external hard drives we've tested.

The Western Digital MyBook comes in a very sleek design that is shaped like a medium-size book and weighs about the same. It features a button in front that activates the bundled Retrospect backup software. The coolest thing about the MyBook drive is that the button has a round, blue LED ring around it that indicates the amount of space available on the hard drive.