Saving the universe, if you're not careful about how you go about it, can become a full-time job - one of those things that looks like it's achieved, but never quite gets done and dusted. For example, imagine you've just finished putting the kibosh on an evil alien plot to use an ancient, artificial ring-world to wipe out all sentient life in the galaxy. You're feeling pretty good about yourself, your feet are up and there's a nice cold drink in your hand and then, suddenly, out of nowhere, you find yourself right back where you started, facing an extra-terrestrial menace much more advanced than your own kind on a do-or-die mission to completely annihilate your species. And all you did was take your eye off the ball, just for a second. Being a galactic, alien-slaying hero can be exhausting. Of course, thanks to Bungie and Microsoft, you can now do it from your own home without lifting a single butt-cheek off the couch. And with the advent of Halo 2 on the PC, the world of Master Chief is now open to many more gamers.

First off, let me clarify something: Halo 2 rocks. Anyone who has ever touched an Xbox has more than likely played at least the first game, and if you haven't - what the hell is wrong with you?! Halo did for the first person shooter what Scream did for the slasher flick and gave it a much-needed overhaul. Only in this case, developers Bungie and Microsoft took a genre that was getting slightly old and limp, injected it with pure adrenalin, strapped an enormous gun to its arm, slapped its face three times to make it angry and then unleashed it on an unsuspecting world. To quote Al Pacino: "Blammo!" was the result.

The story behind the first Halo was a very simple yet engaging sci-fi tale. Set in the distant future, Earth is locked in a desperate war against the forces of the Covenant, a group of deeply religious alien races who are waging a holy crusade against humanity. To combat the much more powerful and advanced Covenant, human intelligence develop an engineered super-soldier code-named the Spartan. These soldiers are encased in a high-density, fully maneuverable battle suit and enhanced mentally, physically, biologically and genetically. Unfortunately however, those pesky Covenant launch an attack on the planet Reach, wiping it out, along with almost all of the Spartans. Now only one remains, enigmatically known only by his rank of Master Chief. You take on the role of this determined, heroic and hard-as-nails super soldier when the ship you're on is forced to crash land on an artificial "ring world" known by the Covenant as "Halo", which is where, in true FPS fashion, all burning hell breaks loose.

The sequel follows on from the destruction of Halo at the end of the first game, opening with an award ceremony that takes place on an orbital platform above Earth, thrown in honour of the heroes of the Halo battle. However, these celebrations are interrupted by the arrival of the Covenant, who it seems have finally discovered Earth's location. Battling his way through the boarding troops on the orbital platform, the opening level, which despite being something of a tutorial, makes for an explosive start, quite literally, when Master Chief defuses a bomb before leaping into the Earth's orbit during a huge space fight, planting the bomb on an enemy vessel, then landing quite spectacularly on the back of a gigantic Earth cruiser. Eat your heart out James Bond! However, the Covenant have made it to Earth and the city of New Mombasa is ready to fall. Only one man can save the day; well, two men, actually, and one of them is an alien.

Halo 2 takes the excellent gameplay of the original and introduces a range of new features, such as duel-wielding and hijacking moving vehicles. The standout innovation though is giving you control of a character other than the Chief, a former Covenant Elite commander who's stripped of his rank for allowing Humankind to destroy Halo. Known as the Arbiter, a revered title but one that is as good as a death sentence, this sympathetic anti-hero is charged with hunting down and destroy a traitor know as the Heretic, an Elite who has broken away from the religious teachings of the Prophets, the Arbiter's journey makes up several of the game's levels. Lots of fans - myself included - found the inclusion of a playable Covenant Elite a travesty. If Halo taught us anything, it taught us to hate the Covenant. We don't want to be them - we want to crush them. With that said, this bold move does open up a much more detailed storyline than the first game and gives a deeper insight into the back-story of the greatest enemy of humankind.

Even though released three years ago and on a last-gen console, the animation and graphics showcased in Halo 2 are amazing. The Covenant Elites are a frighteningly-realised bunch; eight feet tall and graceful as armour-plated cats, their animation is lifelike and a wonderful contrast to the two new additions to the Covenant forces, the ape-like Brutes and the insectoid, airborne Buggers. Each level is beautifully realised, lovingly crafted and every care has been taken to bring the world to life. As you race towards the nearest available cover, chunks of rock and debris chipping under the onslaught of Covenant gunfire, it's easy to immerse yourself in these virtual war zones. Angling the camera upwards at the glorious blue sky or the star-spangled cape of night, it really is a challenge to stifle a gasp. The opening few levels make one of the most stupefying introductions to an FPS that I have experienced, as seemingly free-thinking AI-controlled marines bark orders to and fro, offer you life-saving advice and even allowing you to switch weapons with them, while in the background a huge walking battle tank known as a Scarab lays waste to the city. And, like all huge and apparently indestructible enemies in the FPS genre, the Scarab just makes you ache for a dust-up with it, something the game later delivers with aplomb.

The sound effects are a mix of inspiring, heart-lifting orchestral numbers and fast-paced suspense music that gets the pulse racing without you even realising it. The sounds of the war raging around you are as real as a week in Beirut and add yet more realism to a storyline that is helped greatly by impressive voice-acting and competent scripting. The best example of this is the undeniable chemistry between the Master Chief and Cortana, the sultry-voiced AI computer program who acts as his advisor throughout both games.

As with the first game, much of the fun Halo 2 offers is derived from joining forces with a friend for the awesome co-op mode and ramping the difficulty right up to Heroic or Legendary. Do that and you're in for a long, mayhem-filled night of gaming. The change of difficulty above normal setting almost creates a different game, as suddenly it takes whole clips to put down the Elites and one wrong move will get you instantly splattered. Standing back-to-back with a mate, each clutching two sub-machine guns and screaming manically as you pump round after round into the advancing horde, is so addictive that you'll find yourself losing whole chunks of days to the grimly satisfying violence of Halo 2. [I've lost count of the number of times I've played through the two games in co-op and single player, but it's somewhere around thirty!! Master Ed.]

Something that lifts both Halo games above other shooters on the market - even recent releases - is the AI. It's easy to believe that the enemies really want to kill you, and they work as a well-organised team in order to do so. This brings a level of much-needed realism to a game based in such a science-fiction setting and really adds to the fun. Enemies you have to outthink are so much more interesting than enemies you can just charge and hit 'til they go down.

The Warthog, Halo's trusty combat jeep, makes a welcome return to form, as do the Covenant's Ghosts, rocket-fast hover-bikes that proved such a nuisance in the first game. But now, not only can Elites hijack Warthogs, but you can hijack their vehicles - while they are moving! Never has a game made you feel quite so much like Bruce Willis or Sly Stallone; as a Ghost roars towards you, precise timing and a press of the A button or space bar makes the Master Chief leap up onto the bonnet of the oncoming vehicle, kick the pilot to the asphalt and assume driving position. Believe me, even after the first 500 times you do this, it doesn't get tired. Try jumping onto the bonnet of a Wraith (the Covenant's hover-tanks) and pounding the exit hatch open before slinging a grenade inside in true action-hero style. It send shivers up your spine. Another nice touch is that you don't always have to be the driver - when you hear the call for a gunner assume the position, rifle to shoulder, you can let your UNAC Marine chauffeur sling you around the streets of New Mombasa like a crazed gun-toting madman. There's even a new version of the 'Hog mounted with a rail-gun, while the classic Scorpion battle tank makes a return with faster reload times, along with the Banshees, the Covenant's light attack aircraft, all for your joy-riding pleasure. The Banshee has a few new tricks beneath the hood too, with evasive barrel rolls, loop-de-loops and a turbo boost.

The multiplayer aspect is one of the most impressive and addictive facets of the Halo games. With such a diverse range of maps and game modes, the multiplayer is almost a game on its own, and what Halo did well, Halo 2 takes to the next level. The Xbox version sported 21 different multiplayer maps, each one set apart from the one before it, and with Xbox Live plugged up you could waste literally days of your life going head-to-head with strangers from all over the world. [Yep, I've wasted a lot of days on this over the years! Ed].

The cross-platform multiplayer offered by Windows Vista is a new innovation, although still suffering the bugs and glitches of all new software, which brings Xbox Live gamers and PC-owning Halo fanatics together in one glorious free-for-all arena. Microsoft have included a couple of new maps taking the total up to 23 - yes, 23! - and the game modes are the same mix of classic King of the Hill and Capture the Flag, with more original modes like the awesome Juggernaut (which pits everybody against one super-powered player, where whoever kills the Juggernaut becomes the new one). The problem is that at the moment, not that many people have Vista and therefore there are too few PC players on the servers. Not that playing against Xboxers is a problem, but if you're an exclusive PC gamer you'll be at a distinct disadvantage against some of the diehard players out there. Obviously if Vista finds its wings and flies, this problem will be remedied fairly quickly. Halo 2 allows up to 16 players per match and the comprehensive browser allows you to choose which match to enter by grouping them by criteria such as number of players and game mode. This makes getting started easy and improves the overall accessibility for first-timers.

The only problem, really, is with a few little niggles that blight a beautiful game. For example, keyboard-and-mousers will struggle with the controls, since they're a direct port of the Xbox version. This, coupled with a stuttering frame-rate that I just couldn't shake despite the goodies under my PC's hood, can make it a very frustrating experience. There's always a risk involved when porting games across the PC-console divide, although porting the Halo games is one risk that many would argue is well worth it. Many of the sequences in the game laboured and were unable to run smoothly. This could be a result of the patches that are automatically installed on start-up, although I didn't suffer enough to warrant any real troubleshooting. Often it's best to manually install patches as a rule.

What you have here is an awesome console game now three years old (but ageing well) that's been given a new home on a platform for which it wasn't designed. Nothing has been tweaked or updated for the change of platform and all that's new is the inclusion of the two extra multiplayer maps. This is a shame since, although the graphics aren't exactly dated, they aren't as impressive as some of the current Xbox 360 and PC releases, plus unless your PC is absolutely state-of-the-art, it may struggle with the more intense fights. If your PC is going to struggle, you at least want it to struggle with ridiculously life-like graphics, not three-year-old last-gen animation. That is the only thing stopping this game from achieving that elusive 10/10 score. A little spit and polish would have gone a long way here.

Despite the inevitable success of Halo 2 on the PC, what I'd really like to see come the advent of Halo 3 is a PC version created to be exactly that, not just a port of a 360 game - a version that utilises the power of the PC and still allows flawless cross-platform carnage, and hopefully even cross-platform co-op. Halo and Halo 2 are the gaming equivalent of The Godfather 1 and 2; although many games imitate them and even rival them, none will ever really top them, and finally all you PC users out there - having already had the chance to play Halo on your computer - get the chance to boot up the sequel and see what FPS gaming is meant to be like.

This is bare-knuckle gaming - big, brash, unpretentious and viscerally entertaining. There's no excessive blood and gore, no gimmicky crime or foul language. This is well-organised, carefully-orchestrated violence supported by some of the best AI you've ever seen, a deep and comprehensive multiplayer mode that creates a game all of its own and a storyline far more creative than your usual terrorist-battling shooter fare. Halo 2 is a triumph, plain and simple and while saving the Universe may be exhausting, its never, ever been this much fun.

Reviewed by Mick Fraser for AceGamez (All Rights Reserved).