Buying a notebook computer? Laurence Blackall says you have to know what you want
Desktop personal computers have become so standardised that choosing the one you want is easy, and there are hundreds to choose from. For most people, the choice is between paying a premium for a famous brand or paying the lowest price possible for a PC whose relatively unknown manufacturer might not be around for very long. But as the cheaper machine will use standard components from well-known and respected manufacturers, the risks seem smaller. If you want a portable or notebook PC, however, it is all very different.

As a notebook PC is only a fraction of the size of its desktop counterpart, all kinds of compromises have to be made in its design. But manufacturers are also investing heavily to ensure their product is different from all the others. Much investment is aimed at improving ergonomics, which have until now been largely the result of a trade-off between portability and functionality.

When we decide to buy a notebook computer, we do so for one of two reasons. Either because our jobs and lifestyles require us to use a computer in a variety of different locations; or because we love hi-tech gadgetry. But whether we are "mobile knowledge workers" or gizmo freaks, we all have to think longer and harder about our choice of notebook PC than our desktop computer. Here are 10 points to consider when buying your next notebook:

1 Price: decide on your budget in advance, and when you look at prices, make sure you know what they include. Does it include a case? How much memory does it include? Most PCs come with a miserly standard 4mb of RAM, which is barely enough to run most Windows applications. Is the standard configuration adequate? Does the price include software you do not need?

2 Screen: think long and hard about this. Monochrome screens are much less expensive than colour and use up a lot less power. The best colour screens, TFT (thin film transistor), are pounds 500 more expensive than Dual Scan colour screens. How long will you spend looking at the screen? When you are in your office, will you plug in a full-size monitor? Look at the actual products and try them out.

3 Keyboard: get this wrong, and it will cause you even more grief than a poor screen. Some notebooks have palm rests, some don't. Often the palm rest has been designed at the expense of key size. Look out for full- size keys and avoid eccentric keyboard layouts. Watch out for keyboards where the "enter" key and space-bar are too small.

4 Pointing device: this is the notebook equivalent of a mouse. The most popular device still seems to be the "trackball", a ball built into the case (or bolted on to it, on most Toshibas). But even Toshiba is adopting the IBM-pioneered TrackPoint device, a miniature joystick located in the middle of the keyboard that for many users provides a greater level of control over the cursor than trackballs. Also gaining in popularity is the TrackPad, a screen-shaped, touch-sensitive membrane that you operate with your finger.

5 Size: it really does matter, and so does weight. Ask yourself these questions: Do you need an internal floppy disk drive? Could you work with a much smaller screen? How small a keyboard can your fingers operate? The lightest models, such as the Compaq Aero, have usually sacrificed the internal floppy disk drive, but you have to look hard to determine which other compromises have been made.

6 Battery life: battery technologies are bewilderingly different and incompatible. If you need to use your computer for the whole of a transatlantic flight, you might consider Lithium Ion technology. Nickel Cadmium (NiCad) and Nickel Metal Hydride (NiMH) are the most frequently found - and cheaper - options, but both have the drawback of the "memory effect"; your battery has to be completely discharged before you can recharge it, or it can damage its performance.

7 Connectivity: to what, if anything, do you plan to connect your computer? Some manufacturers offer a limited range of "docking stations" into which you can slide your computer, to connect it to, say, your office network, printer or external screen and keyboard. Multimedia docking stations currently feature CD-Rom drives, speakers and an abundance of options. A simpler but none the less elegant solution is the port replicator; this is a snap- on device to which you can keep all your office-based peripherals attached, without making your desktop look like Nasa's mission controlroom. Nearly all notebooks now come with at least one PCMCIA slot. This allows you to plug in either a network adapter, which will give you access to all network-based resources, or a PCMCIA modem. Ultimate, hassle-free connectivity comes courtesy of infra-red technology. An infra-red port on the rear of the newest notebooks can - if the corresponding peripherals are similarly equipped- give you a cable-free desktop.

8 The processor: this determines the power of the computer. Whatever you buy today will look as old-fashioned as flares in a couple of years time. So how much do you need that pounds 200 more expensive processor? Only time will tell. If you really use your PC for only the most basic tasks, and your budget is limited, spend the extra money on memory. Remember that processor prices halve every 18 months: only buy more power if you really need it.

9 Drives: unless your main aim is weight reduction, get a machine with a built-in floppy drive and select the biggest hard disk you can afford. It is easy to underestimate how much disk space you will need, so go for the most you can afford. The modular design of many notebooks does mean you can swap hard disk drives, and PCMCIA technology means that you can add an extra miniature drive. If you really need mobile multimedia, a growing number of manufacturers are incorporating CD-Rom drives into their machines. But the penalty in weight, battery life and price is substantial.

10 Warranties and service: these are aspects of computer buying that are often sacrificed to price by the home user. Think very seriously about where you will be using your computer before you decide what kind of service package you will need. For example, how convenient is a "return to base" arrangement when you are in Guernsey and the base is in Shannon? Look for on-site service throughout the guarantee period, and consider carefully the extended warranty options. If you travel, buy from a manufacturer with an international service arrangement.