For the past year-plus, netbooks have been flooding the market. They champion mobility and the best possible battery life. Their displays are rarely larger than 10 inches and the processor is often an Intel Atom. And of course, for maximum mobility, like some laptops, they have no optical drive. This can be a problem when it comes to installing software. Rather than converting everything to saved images and using a program like Daemon Tools to mount them, a small, inexpensive external DVD burner is a great alternative.

USB powered

All so-called ''slim'' drives are powered via the USB port, so they don't need to be connected to an AC outlet. There are different approaches to powering the drives. Buffalo Technology, for example, and Samsung use a USB "Y" cable, whereas LG supplies two separate USB cables. The first carries the data and also powers the burner, and the second provides additional power if needed. In both cases, if your computer's USB port provides enough power for the drive, you don't need to plug in to a second port.

Three factors to consider

In terms of actual use, the main point to consider is the noise the burner makes while operating. While it's hard to find a "silent" optical drive, some are noisier than others. There are differences of up to 4 dB between products (and this is more than noticeable).

Weight and size are also criteria that should be considered. External drives are designed to be carried around with a netbook. So they have to be as small and as lightweight as possible.

A final point is how they look, but since this a matter of individual taste, we won't take it into account in our ratings.