• Mobility -- for those who need to use their computer on the road, small, light, energy-efficient laptops with a long battery life are essential.

• Multimedia -- laptops that may or not need to be portable, but which will run intensive photo, video or music editing software for professional users.

• Desktop Replacement -- an increasing number of people are choosing to replace bulky desktop PCs with powerful laptops.  Mobility is less of a concern for these users, who want to get the best performance out of their computer in one, or maybe a handful, of locations.

• Gaming -- faced with similar constraints as those who opt for a desktop replacement laptop, gamers tend to use their power-hungry laptops in a single location, emphasising high-end hardware such as dedicated graphics cards.

For each of these different categories of laptop consumer, we've offered an up-to-date recommendation of a minimum standard you should aim for each type of hardware component:

• Processor

• Hard Drive

• Memory

• Graphics Card

• Screen

• Battery

• Optical Drives

Processor

The processor is at the heart of any computer, but they're more often described as the brains of the machine. 

They are responsible for everything you do with your computer and so affect the speed with which you work or play. 

Several factors combine to determine the speed of your processor.  Its basic speed, measured in MHz or GHz describes how many operations it can handle per second, and is complemented by the size of its cache, a special type of memory always immediately available to the processor, and how many cores it has. 

Multiple core processors effectively bundle several processors tightly onto the same chip, resulting in improvements in speed and multitasking.

Are multi-core processors worth it?  In theory, they allow for faster execution of programs by offering more processing power, but for this to be effective, the software has to be redesigned to be compatible with multiple processors. 

Not a lot of software is ready for multi-core processors yet, and so it's not worth rushing out to buy an expensive quad-core processor if the programs that you want to use with it won't feel the benefit. 

Having said that, though, they do allow more effective multitasking by running one program on each core, so if you are likely to run several programs at once they can be useful.

Some tasks require a lot more processing power than others, so think about how many of the following you're likely to want to do when you consider your processor:

• 3D animation
• encoding video or audio files
• editing images

As for gaming, it's not so much the speed of the processor that's key but the graphics card, which is more often the sticking point. 

If you're on a limited budget, it's definitely worth going for a powerful graphics card and an average processor rather than the other way round.

Just as choosing a large, high-resolution screen can bring with it the downsides of a large, unwieldy laptop, choosing a powerful processor can have physical downsides too. 

More powerful processors use more power, and get hotter more quickly, meaning your battery won't last as long.  If you plan to keep your laptop on your desktop and plugged in, then that shouldn't be a problem, but having a processor that's more powerful than you really need can create problems if you're forever running out of juice while you're on the road.

Here's what we recommend for different types of user (see the box on the right):

• Mobility Dual-core processor with good power consumption

• Multimedia Dual-core, or perhaps even more

• Desktop replacement Dual-core processor with good power consumption

• Gaming Dual-core, the more powerful the better.

Hard Drive

If the amount of space available on hard drives is constantly rising, then so too is demand: software, photos, music and video are all taking up more and more room. 

As with processors, a lot of different factors come together to define how well a hard disk drive performs, but it often ultimately comes down to how much room there is on the disk. 

The number of platters that combine to bring together this space, as well as the speed with which the platters rotate also contribute to its overall performance, but its often hard to get your hands on this data.

If you can find these technical details, then go for a disk that spins at least 5200 rpm, or 7200 rpm if you can. 

Knowing whether or not your hard drive is going to be noisy is something else which is hard to find out beforehand, but finding a quiet disk is really worth the research.

Here's what we recommend for different types of user as a minimum (see the box on the right):

• Mobility 160 GB

• Multimedia 250 GB and possibly an external hard drive for extra media storage

• Desktop replacement 160 GB

• Gaming 250 GB

Memory
A computer's memory, or RAM, for Random Access Memory, is kind of temporary clearing house between the processor and the hard drive. 

It's random because it allows any kind of information to be stored anywhere, unlike your hard drive or a DVD, which both store data in a continuous way, gradually filling up the disc so that moving parts - a spinning disc, for example - are needed to find the relevant piece of information. 

The purely electronic storage offered by RAM is much quicker, which is why it's used for the temporary storage of data that is currently in use.

The one key question that you need to ask about the RAM in your laptop is just how much of it there is.  Our tests with Windows Vista suggest a big improvement when upgrading from 1 GB to 2 GB of RAM, and a more subtle increase in performance when moving up again to 4 GB. 

Go for 2 GB if you can, but if you can't, don't worry, as adding RAM to a laptop is one of the few upgrades that end users can normally make.

As with processors, other factors come into play, such as how fast the RAM can be activated, and, if you are thinking of adding additional capacity, you'll also want to know what size and shape of chip that you'll need to buy to add to your laptop.

Amongst others, Crucial provide a great service allowing you to check exactly what RAM is compatible with your laptop.

In terms of a solid basic specification, here's what we recommend you look at:

• Mobility 2 GB

• Multimedia 2 GB; 4 GB for complex image and video editing

• Desktop replacement 2 GB; 4 GB if loading your computer quickly is important

• Gaming 2 GB; 4 GB will improve game speeds, but not necessarily graphics

Graphics Card

Laptops either have a modern, dedicated graphics card that will allow you to get the most out of recent games, or they don't, it's as simple as that. 

This second category instead feature what's called an integrated chipset, essentially meaning the processor handles graphics as well as everything else, meaning there is less clout behind images than there would be if there was a dedicated piece of equipment dedicated to the role.

Even laptops with an integrated chipset can use the new Aero features in Window Vista, and it's really only gamers who need to worry about ensuring they have the most powerful graphics capabilities.

Although there is a growing trend for more and more 'ordinary' applications to use the graphics card, for the time being its use as a separate component is largely confined to games.

Here's what we think different types of user will want to look at (see the box on the right):

• Mobility integrated chipset

• Multimedia integrated chipset or an average graphics card

• Desktop replacement integrated chipset

• Gaming powerful dedicated graphics card

Screen

Choosing the right screen is one of the most important decisions when you're looking for a new laptop. 

The are two elements to consider: the physical size of your screen, and its resolution, or the number of pixels it has. 

Obviously, the bigger your screen, and the higher the resolution, the more information you will be able to access at once, and you should go for the best screen you can afford.

There are two factors that you should bear in mind, however, that may well convince you to economize slightly by going for a smaller screen.

The first is how easy it is to carry the computer, which is an obvious consideration.  Bigger screens are heavier and, by definition, harder to carry. 

The second factor is how powerful the graphics card is.  Higher resolution screens can show more information and more detail because they have more pixels, but this requires more processing power. 

In general, consumers can be divided into two groups according to how powerful a graphics card they need. 

On the one hand, for the average office user, increasing the resolution by 30% by passing from 1280 x 800 pixels up 1440 x 900 doesn't necessarily require a large improvement in graphics performance and is normally very worth it.

For gamers, on the other hand, processing the extra 300, 000 or so pixels is a big challenge and they need to make sure they secure a laptop with the most powerful graphics card available.

One last point about choosing your laptop screen concerns the coating over the screen itself. 

Two options are available, either matt or glossy, but the consumer marker has recently - and unfortunately - been swamped with glossy screens. 

It's a real pain because, although they supposedly offer better colors and are easier on the eyes, it's often impossible to see the improvements in quality without getting distracted by your own reflection.  We can't make it any clearer: get a matt screen!

In general, our screen recommendations are as follows (see the box on the right):

• Mobility 13" screen, 1280 x 800 resolution

• Multimedia 15'' screen, preferably widescreen

• Desktop replacement 17'' screen, as high a resolution as possible

• Gaming 17'' screen, as high a resolution as possible

Battery

When looking at laptop batteries, there are two key numbers that you need to look out for: voltage and capacity, which will allow you to make a rough estimate of how long it will last. 

A lot of manufacturers talk up the number of cells their battery has, but this isn't relevant in determining how long your battery can go for between charges: it's just a description of its internal structure.

The power consumption, measured in Watts per hour, can be found by multiplying the voltage by the number of Amps per hour. 

So, a 1800 mAh (= 1.8 Ah) 10.8 V battery gives 1.8 x 10.8 = 19.4 Watt-hours. 

Then you need to look to see how much power your computer uses to see how long the battery will last.  If it's, say, around 10 Watts per hour, then this hypothetical battery will manage to last around two hours.

The length of time that a battery lasts increases if the demands placed on it are stable and regular, rather than periodic. 

Think of how quickly your digital camera uses up its battery - that's because the flash requires very large bursts of power very quickly, which uses up the battery much more rapidly. 

The same phenomenon can affect your laptop battery, so think carefully about which applications you are likely to need to run, and how often you might be using your laptop on the road and reliant on its battery.

It's difficult to talk in exact numbers when making reccommendations about laptop batteries, so here are the factors that each type of user might want to look at (see box on the right):

• Mobility The best compromise between weight and battery life.

• Multimedia Powerful battery to provide enough juice for video and audio.

• Desktop replacement The one configuration in which you can forget about the battery!

• Gaming Given the high power consumption, you're unlikely to actually use the battery for gaming.

Optical drives

Opinion is divided on whether or not computers will still include optical drives to read CDs and DVDs a few years from now. 

Apple's Mac Book Air created something of a stir last year, for instance, by leaving out this component which was until relatively recently considered pretty essential. 

With the increasing trend towards downloading films, music and software, many people are beginning to wonder whether or not dedicated optical drives are actually necessary, especially given the high power consumption required by their moving parts.

For the time being, though, it's probably best to hedge your bets.  Indeed, that's most manufacturers are doing, but given the variable quality of optical drives available, it's worth making sure you get a good one. 

In particular, the fact that the DVD player is often the noisiest part of a laptop can cause problems if you intend to use it either at work or for watching films.

Adding a Blu-Ray DVD drive to enjoy HD content on your computer is a tempting option, of course, as coupled with an HDMI output it could even allow you to ditch a separate DVD player in the front room. 

Two reasons to avoid this seductive offer are the added cost involved, for the time being at least, and the fact that Blu-ray DVD players can be slower at reading data discs.

The ability to burn DVDs is now more and more common, and wherever possible you should try and opt for a double-layer DVD writer to cram up to 8.5 GB of data onto just one DVD.

In general, our recommendations for optical drives for different types of user are as follows (see the box on the right):

• Mobility external DVD writer to save space

• Multimedia double-layer DVD writer and Blu-ray drive

• Desktop replacement double-layer DVD writer

• Gaming double-layer DVD writer