XP IS GETTING a bit long in the tooth, Vista is a pig and you don't want to buy a Mac and join the Jobs Cult. So, you're thinking of having a look at Linux, but are bamboozled by the hundreds of flavours and don't want to spend a weekend discussing it with disturbingly intense bearded men in socks and sandals. So here is the Inquirer's guide to Linux: quick, clear, opinionated and unfair.

There are scores and scores of minor players but only about half a dozen big ones that are worth looking at. We'll ignore all the single-floppy efforts, mini-CDs, routers and firewalls, security toolkits and so on, because they're specialist and there are too many to enumerate.

Which leaves the big, general-purpose distros, the one-size-fits-all, do-anything offerings. But first, ask yourself some questions. Are you willing to pay? If so, a bit or a lot?

Another significant difference is the desktop. Basically, there are two, both fairly Windows-like. GNOME is simple (some say too simple), clean and in places very slightly Mac-like. KDE is fiddlier, perhaps even cluttered, resembles Windows a bit more but offers more opportunity to tweak and customise. Your choice.

Also, it's worth saying: if you tried Linux a few years ago, it's time to take another look. In the Free software world, things move a great deal faster than in the big commercial software houses: releasing a new version every two years is seen as slow, stately and considered and several distros put out a fresh edition twice a year. Linux knowledge from last year is old-fashioned and from a few years ago is positively ancient.

So, in strictly alphabetical order...

Debian
Debian is the daddy. It's one of the oldest surviving distros, partly because its designers thought hard about the software packaging problem way back when, sorted it and moved on. It has few frills, but it does offer a vast selection of applications, focused on capital-"F" Free code. The snag - well, it's not exactly renowned for its user friendliness. If you need the advice of this article, you don't want to mess with Debian.

Fedora
You hear a disproportionate amount about Fedora, because it's American. Development is sponsored by Red Hat, the US Linux giant. Red Hat used to give away its eponymous product for free. Since 2003, though, it's gone for the enterprise market bigtime. The free OS disappeared, replaced by Red Hat Enterprise Linux which costs big bucks. It's well-liked by the sort of suits who think that unless you paid more for the software than you give each month to the poor sods who maintain it, it can't be worth anything. RHEL is what you want if you took out a maintenance contract on the office loo. It's safe, reliable and staid.

If you want to try it for free, though, there's CentOS, compiled from the source code to RHEL, which Red Hat makes publicly available.

To fill the gap left by the end of the official free version, Red Hat created Fedora. It's a sort of free rolling technology testbed for stuff Red Hat might stick into the grown-up version later. With two releases a year, we'd call it an ongoing beta except that it's had some distinctly alpha-ish moments. It has lots of enthusiastic and helpful users, so you can get help fairly easily. For years, the official software installation tool, the Red Hat Package Manager, RPM, was very poor, lacking facilities that rivals had had for a decade, but it's catching up now with more advanced from ends like Fedora's YUM.

One problem shared by many free Linux distros offered in the USA and certain other jurisdictions is that they can't legally give away for free proprietary tools like MP3, Flash and Java - so out of the box, you can't open these kinds of files. A sign of the corporate mindset behind Fedora is its solution to this problem: it tells you where to go to buy licensed commercial versions. Very helpful.

Gentoo
Gentoo is the distro for those who disdain Debian and Slackware for being too easy. The idea is that you compile it all yourself from source, so ending up with something perfectly tailored to your hardware. Think Vauxhall Nova with plastic body kit, LEDs in the screen jets, an exhaust you could stick your fist up and a boot full of bass speaker.

Linspire, Freespire
Linspire is a shiny colourful desktop distro aimed at the pile-'em-high, sell-'em-cheap market. It's designed to be basic, really easy to install and to closely resemble Windows. Indeed, it used to be called "Lindows" and offered a built-in - and somewhat ropey - facility to run Windows programs, until Microsoft sent the boys round. It used to be based on Debian, but more recently has moved to Ubuntu - more on that later. It doesn't come with much software included - it was cheap and the company hoped you'd buy extra apps from their online "warehouse", where they sold an assortment of software that's mostly free anyway. There's a free version now, too, called Freespire, and much of the contents of the online store is free these days too. Both flavours are pretty good on the proprietary codecs and drivers front, but it's a relatively minor player.

Mandriva
Mandriva used to be called Mandrake until its makers bought Brazil's Connectiva. Not much of the Latin Americans' technology survived but a couple of syllables of the name did, so that's all right. Mandrake started out as "Red Hat with KDE", when Red Hat was still free and the dominant distro, and KDE was the trendy new desktop GUI, which Red Hat didn't offer because bits of it weren't entirely Free. Nowadays, though, Red Hat does offer KDE, since which time, Mandriva has set out to distinguish itself as the friendliest Linux. It doesn't always make it but it's a good effort. The main product is commercial and updated annually, but there are free single-CD GNOME and KDE editions. The success of the company's efforts at simplification and polish can be judged from the fact that there's a free spinoff of it called PCLinuxOS, designed to make it more polished and easy.

Slackware
Slackware is another survivor from the early days, like Debian - and similarly is best left for the beardies. Compared to the others, it's dead basic - its startup files and software packages stick to ancient Unix methods, avoiding the trendy bells and whistles of younger Linuxes, although it's gradually gaining some modern features like automatic updates.

SUSE
Novell has got into Linux in a big way, by acquisition - notably, GNOME programmers Ximian and German distro producers Software- unt Syst em-Entwicklung, or SuSE. Now, SUSE is Novell's brand of Linux. Formerly a heavily-KDE-based distro (KDE was also a German project at the start), SUSE was best-known for its inexpensive commercial product SUSE Linux Professional, a big boxed set with umpteen CDs and DVDs containing everything you could ever want and pretty decent dead-tree manuals. Novell's changed all that and now follows a more Red Hat like strategy.

Broadly, there are four lines. Open Enterprise Server is " reassuringly expensive" and bundles Netware services on top of a Linux server, which is also available rather more cheaply on its own as SUSE Linux Enterprise Server (SLES). There's also a client, SUSE Linux Enterprise Desktop (SLED). Basically these are the core, most tried-and-tested bits of the distro, bundled with support, updates and so on. New releases come every two or three years, to suit sluggish corporate timescales.

For cheapskate home users, there's openSUSE. (There are free evaluation versions of the enterprise products, but since Novell doesn't offer free updates, in effect they're sort of time-bombed demos.) You can download either a GNOME or KDE edition as a single CD image, or a DVD image with both, or buy it as a boxed set with media, manuals and a few months' support. If you opt for the CD, there are lots of additional components online. OpenSUSE is rather sleeker than the old boxed set and it comes with some codecs preloaded. Like Mandriva, it's based on RPM and new releases come roughly annually.

Ubuntu
Ubuntu is the brown one, possibly because it's got a tan from hogging all the limelight. The name is African, untranslatable from the isiXhosa but roughly m eaning "be nice to people for a change". It was set up by a young South African called Mark Shuttleworth who became absurdly rich by setting up a dot-com and selling it to Verisgn at exactly the right time. After a US$20,000,000 trip to the International Space Station, Ubuntu is what he did next, more or less his way of giving something back.

Shuttleworth's original plan for Ubuntu was straightforward and similar to that of the abortive UserLinux project: to pick one best-of-breed program from each main category of application - desktop, web browser, office suite and so on - and bundle them up with Debian into a single CD, so there were no confusing choices or options when installing. The team picked GNOME as an easy, all-Free desktop.

KDE has a massive following of its own, though, and a version of Ubuntu based around KDE and KDE applications instead of GNOME quickly followed. It's called Kubuntu and has been officially adopted as a sister product, as have several other spinoffs from the many as-yet unofficial derivatives. The GNOME version is still the official main product, though, with a distinctive look based on shades of brown and orange, African imagery and sound effects.

Ubuntu is still a little raw in places - both SUSE and Mandriva have better setup and admin tools, for instance - but with two releases every year, it's maturing very fast. It's a smooth, polished desktop OS, with decent driver support. Due to its Debian roots and good design, software installation easier than on any rival operating system, Macs and Windows included. The project hosts a collection of many thousands of applications on its web servers and you can install any of them by ticking one box and clicking OK. This includes a single package called "ubuntu-restricted-extras" which adds support for MP3 and other proprietary formats with just two mouse clicks.

Sponsored by its multimillionaire founder, there are no commercial or paid-for versions of Ubuntu: all flavours are completely free. The company will even ship you professionally-made CDs for no charge if you don't fancy downloading and burning your own. The plan is that ultimately the company becomes self-financing by selling support and consultancy services to corporate customers.

Xandros
Xandros is the OS you will meet if you buy one of the Asus EEE super-cheap mini-laptops. A distant relative of Linspire, it's another Debian derivative, originally developed and sold by Corel as Corel LinuxOS, arguably the first really simple, pared-down desktop Linux for non-experts. It's still commercial, although a slightly dated and slightly limited free demo CD is available for download. There are several editions, aimed mainly at corporate and business desktops, with a new Server variant that comes with an MS Exchange-compatible groupware server. Its main claim to fame is that it goes out of its way to be Windows-like and Windows-compatible. Its desktop is a modified version of KDE with a Windows Explorer-like file manager and it can both join Windows domains and run some Windows applications. A slow, corporate-friendly release cycle means that it's not state of the art, but it's a good choice if interoperating with Windows is your top priority.

Rounding up
Frankly, despite the embarrassment of riches, we reckon the choice is pretty clear. Avoid the geek distros. Fedora is too experimental. Linspire doesn't really have much going for it. Xandros does, but it costs and it's not flashy or pretty. Mandriva and openSUSE are good solid offerings, but Ubuntu has them beat. It costs nothing and you don't lose out on any bonus extras reserved for paying customers. The free online support and help are excellent, too.

Ubuntu first appeared in just 2004, but already it's claimed more than half the "market" according to the Open Source Development Labs' 2007 Survey. It has more than twice as many users as Debian and about three times as many as Fedora or SUSE.

Ubuntu Server is still very basic - big businesses wanting a server should evaluate Red Hat and SUSE and small ones Xandros or the free SME Server.

As for the future - for now, Ubuntu looks unstoppable. Give it a go.

First time around, don't use a laptop - use a desktop machine with a wired network connection. Don't dual boot it if you can avoid it - use a PC you can wipe clean. Don't try something state of the art, as there may not be free drivers yet. Most hardware vendors are too selfish to provide free documentation for open source developers, so everything must be reverse-engineered. You don't need much - just the same sort of spec as for XP. Half a gig of RAM, although more won't hurt, a 2GHz CPU and 20G of hard disk will be plenty. It's faster and easier to install than Windows, and once it's on, all your applications will be right there ready to use, and it only ever needs a single online update rather than half a dozen visits to windowsupdate.microsoft.com, rebooting each time.

Look at it this way. It's free. If you love it or hate it, either way, you're guaranteed to get your money back! µ