If you're on the lookout for a new portable PC, it pays to pay close attention to the specifications on offer before you get out your credit card. Not all laptops are equal, and we're not just talking about the inherent differences between different laptop formats, such as netbooks and more powerful desktop-replacement laptops.

Check out our laptop buying advice below to get to grips with the specs on offer and learn the bare minimum requirements for today's portable computers, and then head to our laptop reviews to check out the latest models.

Netbook buying advice

Portability and a lower price tag are the netbook’s main attraction. Speed and comfort are their main problems.

Initially conceived to run Linux from a small internal solid-state drive, the netbook category was soon overrun with near-identical designs locked-down by processor and OS suppliers Intel and Microsoft.

Essentially all netbooks now take an Intel Atom, run Windows 7 Starter; and have a 10.1in low-resolution 1024x600 screen, 1GB memory, 160GB/250GB hard disk, and three USB 2.0 ports.

Following the success of the Apple iPad since its launch in 2010, the category is on the wane, and may decline further, especially if other types of tablet PC prove popular.

Processor: Intel’s Atom is the de-facto netbook processor. It consumes little power and gets the job done eventually. Expect sluggish navigation and slow startups. Look out for AMD’s new APU chipsets in 2011, a combined CPU/GPU solution that fianlly promises competition for Intel in this low-power processor class.

Storage: Early models had small flash-based drives up to 8GB. Now, effectively all netbooks come with either 160GB or 250GB 2.5in SATA hard-disk drives.
Memory: Windows/Intel (Wintel) netbooks are restricted to 1GB of RAM, but you can easily upgrade this yourself to 2GB for around £25. That’s our recommended minimum for running Windows 7, and will help prevent the netbook slowing further as apps are opened.

Wireless: 802.11b/g was the original standard wireless card in netbooks, but most newer models support 802.11n now too. Faster Wi-Fi technology won’t affect browsing speed but will come in handy when transferring large files. All the models currently in our chart support 802.11n

Bluetooth can be useful but is not always a standard fitting. Some netbooks also include built-in 3G modems, needing just a 3G SIM card to gain wireless internet outdoors.

Operating system: Earlier netbooks were equipped with a Linux operating system. Windows 7 Starter Edition is now standard, with slightly reduced performance compared to Windows XP.

Display: Dependence on slower integrated graphics means netbooks are not great for gameplay. The Atom processor allows standard-definition video playback, but to play HD video, you’ll need a netbook that can offload this duty to the graphics processor (‘hardware-accelerated video’).

Keyboard: Cramped keyboards go with the territory, and it’s useful to try out typing on a netbook before you buy it. For keyboards on the smallest netbooks (9in screen in less) touch-typing will be impossible. Watch out for non-standard layouts of some keys; and netbooks sometimes sacrifice dedicated function keys.

Extras: You’ll find few extras - don’t expect to find a DVD drive, FireWire port or ExpressCard slot, nor recent additions like USB 3.0. You’ll find three USB 2.0 ports, often crammed closely together. This can prevent two larger thumbdrives from being inserted alongside each other, for example.

Laptop buying advice

Processor: Intel chips remain the dominant force. While some Intel Core 2 Duo processors are still in circulation, most modern laptops currently take Intel Core series chips. Quad-core processors are becoming more acceptable since the arrival of the latest second-generation Core series (Sandy Bridge) processors. Efficiency has improved enough that they’re no longer crippled by heat and battery-life problems.

Processors in Intel’s Core i5 and i7 (and also the i3) families include performance features such as Turbo Boost, for short-term overclocking; and Hyper Threading, which makes a dual-core processor perform more like a quad-core processor. There’s no logic to which processors contain which technology; and beware that some older Intel Core i7 mobile chips are only dual-core. Check specs first if you need a certain feature.

AMD also makes processors for mobile computing, often found in budget full-size laptops. Efficiency tends to be lower, meaning more heat and noise and shorter battery life.

Memory: The minimum amount of RAM commonly fitted is now 2GB. Aim for at least 4GB, although Windows cannot use more than 3GB in its 32-bit versions. If you have 4GB or more of memory, go 64-bit.

Hard drive: The hard disk is still the most popular storage type for laptops, even if solid-state storage is the preferred solution for portables.

A 5400rpm drive from 250GB to 750GB capacity is typical, although capacities of the smaller 2.5in SATA disk drives now reaches 1.5TB. A faster 7200rpm drive improves performance, at the expense of slightly higher heat and noise, and lower battery life. It can be awkward to upgrade a laptop’s hard drive, so get as much storage space as you can.

For best performance and increased reliability, look out for a solid-state drive (SSD). Prices remain much higher than hard-disk drives, but if you have the budget the offer of silent operation, greatly increased performance and resistance to shock make the SSD the best choice for mobile computing. SSDs can be found in 60GB to 500GB sizes. If you can afford it, look to 128GB or 256GB capacity. The 500GB remains a four-figure luxury.

Screen: Laptop screens were once all 4:3 ratio, until 16:10 widescreen became popular. Now most laptops take 16:9-ratio displays. Size of screen dictates the overall size of notebook. If you want a small and easy-to-carry ultraportable laptop, look for a display of 11in to 13in.

The 15in screen size is very popular, offering a good balance between available working screen space and a still-luggable notebook.

At 17in or 18in screen size, the laptop becomes more of a static fixture, better suited for designers or for home entertainment use.

Increasing the resolution of the display means more can be crammed into the screen, at the expense of legibility as screen elements reduce in size. A full-HD 1920x1080 resolution on even a large 17in screen can make work difficult due to tiny text and icon size.

For screen backlighting, white LEDs are now popular, reducing power consumption and reaching full brightness instantly on demand.

The issue of gloss or matt finish can be divisive: shiny screens look initially impressive, thanks to their bolder colours and deeper blacks, but their reflectivity causes visibility problems when used in rooms with windows or overhead lighting. Matt screens appear duller but have better off-axis visibility and are unlikely to cause eyestrain.

Also watch out for cheaper screens with severely restricted viewing angles.

Graphics card: For the smallest or cheapest laptops, the graphics processor will be soldered to the circuit board or even built into the main processor chip – both options are so-called integrated graphics.

Integrated graphics solutions such as those from Intel remain popular, as their power consumption is low and they take little space inside small portables. The latest Intel Core series processors’ integrated graphics are sufficient for very basic gameplay; for more realistic gaming, you’ll still need a decent graphics card. There’s no clear choice between AMD (formerly ATI) and nVidia, as performance varies depending on product. For gaming use, look for at least 256MB of graphics memory.

Some laptops feature switchable graphics, using an integrated chip to preserve battery life, and a dedicated graphics card for maximum performance. You’ll find such switching tech available with both AMD and nVidia processors, and for Windows and Mac notebooks.

Operating system: Windows laptops are less predictable when recovering from sleep and usually appreciate shutting down then restarting on each use, a process typically taking several minutes.

For instant-on accessibility, look to Apple’s MacBook portables with their Mac OS X operating system. These also require less maintenance such as file defragmentation, and do not demand resource-hogging anti-virus software.

Interface devices: the rubber-tipped trackpoint was once popular, a small steering stick lying flush within the keyboard. These only tend to feature on some business laptops now. Most notebook computers use trackpad/touchpad sensors to allow the finger to control the motion of the on-screen cursor.

Multi-touch control, once only found on Apple portables, is now appearing on Windows laptops too in basic form. To make comfortable use of muti-touch, look for a decent size touchpad, at least 100 x 45mm.

Beware of low-cost trackpads fitted to budget laptops which can make cusor control difficult. Also consider the click buttons, which may be ill-placed or too stiff for easy use.