With two 320GB disk platters, this 3.5in Caviar SE16 desktop drive is the most densely packed in Western Digital's arsenal. It's aimed at users who want plenty of performance.

With more data located on each platter than in previous SE16 models, it means that fewer platters and therefore heads are required inside the drive. This means the heads can access more data with shorter movements, helping to boost performance significantly. Not only that, but with less platters and heads in the hard drive it should run cooler and with less noise emissions and vibration. The 640GB (596GB formatted capacity) drive features a 16MB cache, NCQ and a 7200rpm spin speed.

The two-platter 640GB density has been achieved by using perpendicular magnetic recording, which gives Western Digital the option of building either single-platter 320GB hard drives for the mainstream market or four-platter 1280GB drives for the upper-end of the enthusiast market. So for now, the 640GB model can be considered a mid-range product as far as capacity is concerned. Its performance, however, places it in the upper echelon of fast desktop drives perfect for gamers and users who work with video or other disk-intensive applications.

In our tests, the drive averaged read and write speeds of 70 megabytes per second and 70.7MBps, respectively, which are both excellent results. Nevertheless, they're still a little slower than premier drives such as Seagate's Barracuda ES2, or even Western Digital's own RE2 (WD7500AYYS), which were tested on the same platform. However, its result in our data copy test (where we copy data from one location on the drive to another) was stellar: it averaged 35.17MBps in this test, which is faster than any of the recent Hitachi, Samsung, Seagate and Western Digital drives we've tested. This means that the Caviar SE16 will be very fast as a scratch disk for Photoshop or for applications that need to compress and decompress data on a regular basis.

You won't have to pay much at all for this drive, either. With a retail price of $169, its formatted cost per gigabyte works out to be a phenomenal 28 cents! It's definitely worth buying more than one and building a RAID array, especially considering the already-quick results we witnessed from a single drive.

Physically, the drive has a 3Gbps Serial ATA interface and there's nothing special about its casing. After one hour of continuous file transfers, the surface temperature of the drive rose to around 36 degrees Celsius, which is much cooler than some of Western Digital's 7200rpm, four-platter drives — such as the RE2 — so it's a good choice for anyone who wants to build a high-performance slim-line or media centre PC. Also in its favour for media centre use is the drive's noise emission, which was very low. Only slight ticking could be heard during intensive data copy operations. Only the most sensitive ears will be able to pick up the drive's sounds while doing things such as using a media centre to record a TV show.

The drive's power consumption was 5.51W when idle and 6.93W during a full load. These low figures are mainly due to the drive only having to spin two platters, instead of three or four. The drive also features optimised algorithms for its heads, which are supposed to contribute to lower power consumption, heat and vibration. The drive's vibration was minimal and typical of what we've noticed with most desktop hard drives.

In the end, the drive's ultra-low cost per gigabyte, excellent performance and cool operation are all very good reasons to buy this drive if you need more storage space for your PC or media centre.