Best Buy is once again selling the Western Digital Passport 320 GB 2.5-inch USB 2.0 hard drive for $149.99. Use a 10% Off Coupon to bring the price down to $134.99.

This is a very good deal for a couple of reasons. First, it’s a small hard drive with huge capacity. It only needs a single USB 2.0 cable to power the drive. This makes it a great Time Machine drive for your Mac.

Even better though, is the fact that you can quickly and easily open the case, and pull out a SATA drive. See, Western Digital is artificially knocking down the price of USB 2.0 drives, while keeping the cost of internal drives high. How do we work around this? A simple credit card will do the trick.

By sliding a plastic card (say, your credit card) into the plastic mold line of the case, you can easily pop the top off. Inside reveals a Western Digital Scropio SATA drive. You can then pop that into any 2.5-inch SATA system. It makes a great upgrade for a MacBook (Pro), Mac mini, or even a PlayStation 3.

You should keep the casing for warranty purposes (if the drive fails, you should probably slip it back in the case for replacement). But, as a nice plus on that end, you can use the drive as an enclosure for any SATA 2.5-inch drive… like the old smaller drive you pull out of your system.

BestBuy.com (Linking to the page isn’t working right now, just type in 8621397 into the search field).

I bought three of these the last time it was offered at $134.99, and I’m about to buy a fourth…

Update: Linked in one of the 10% off coupons. As I was picking up my fourth one of these drives last night, I noticed stores are starting to run slow. These drives use the old packaging, so I would say that it’s fair to call this a clearance… even though Best Buy is marking it down as a silent promotion.

In other words, if you want one, go get it now.

Update 2: As noted elsewhere, there’s one more thing you should do during installation. If you look to the right of the SATA ports, you’ll see a jumper. Remove that jumper before installing the drive. It basically tells the Scorpio to use a special “green” power mode. While the typical green drive is fine, this jumper forces added wait times and slowdowns to ensure that a single USB cable will provide sufficient power. Since that is not needed in a true SATA environment, removing that jumper will give you an instant performance boost.