First of all, let's separate once and for all notebooks and netbooks.  Both can rightly claim to be portable computers, but the target audience and general approach of each is very different.

Plenty of people use notebooks as their usual everyday computer: I'm typing this article on one, and there's even a class of notebooks known as desktop replacements beause of their powerful feature set.

For the vast majority of netbook owners, though, their netbook is a secondary computer, designed to be taken on the road, but not replace their main machine--which might well be a regular laptop or just as easily a desktop computer.

The absence of a DVD drive, the small screen and the cramped keyboard all point to the fact that netbooks are just one answer to the classic trade-off between performance and portability, with the advantage weighing in favor of the latter in the case.

We've looked at regular laptops before, but given the enormous popularity of netbooks, we've decided to launch this new Product Survey.  As a first guide, here are three questions that you'll most likely be faced with when you begin to look at this market:

• Storage: Flash Memory or Hard Disk Drive?
Flash memory has several advantages thanks to the fact it contains to moving parts: it's silent, resistant to sudden shocks and uses very little power.  It's not a silver bullet, though, as the technology is still far from affordable, especially at larger sizes.  For the time being, it tends to be a high-end solution in the smallest, most energy efficient netbooks, with other models retaining conventional hard drives for their extra storage capacity.

• Screen Size: 8'' or 10''?
There's a simple relationship between the size of your screen and how portable your netbook is: the bigger the screen, the heavier it will be!  Measured diagonally from corner to corner as with screens on other devices, a 10'' netbook screen is perfectly comfortable and leaves room for a decent-sized keyboard.  In general though, 10'' netbooks are between 100 and 200 g (3.5-7 ounces) heavier than the other common size for netbooks, 8''.

• Operating System: XP or Linux?
Unlike elsewhere in the computer market, where Windows Vista is increasingly the only option, Windows XP and Linux are fighting it out on netbooks.  Provided the netbook in question has a reasonably powerful processor and at least 512 MB of RAM, XP runs perfectly well, and will bring a familiar environment right into your backpack if you're already a Windows user.  Installing the software and peripherals that you're used to having around on larger computers shouldn't be a problem either, within the limits of the netbook's less powerful performance.

There's more variation with Linux, with most manufacturers customizing an already-existing distribution with the aim of making it more accessible.  Going beyond the basics to install your own software or getting involved with exotic hardware does require a minimum of technical knowledge, and, while there's plenty of help out there on the Internet, there's usually no official tech support.