As most people now know, there are two computer based theory Tests which have to be passed at the same 'sitting':- the Multiple Choice Question Test and the Hazard Perception Test.
The Multiple Choice Question Test currently consists of 50 questions where you choose one answer from a possible four. The current pass mark is 43.
The Hazard Perception Test consists of 14 driving video clips in which you have to identify hazards by clicking the mouse, the sooner you spot the hazard, the more marks you score. Thirteen of the clips contain one hazard, one contains two, with a maximum score of 5 per hazard making an overall test maximum of 75. The current pass mark is 44.
To prepare for the Multiple Choice Question Test there are many books, CD Roms, and DVDs available both 'official' and commercial. The most common mistake is to practise only on these CD roms or to try and learn all the questions (900+ of them!) in the official 'question bank'. The fact is that all the questions are based on information given in The Highway Code, possibly the cheapest publication of all, and if you know that well enough, it won't matter if you've never seen a computer before, you will still know the answers!
Preparation for the Hazard Perception Test is, however, probably best done using CD Roms or DVDs on a computer or DVD player, since the test in it's current form is more of a computer game than real life! Otherwise, look for situations that you might click your mouse at when you are either driving yourself or as a passenger, but if you are the driver, don't forget that it is real life and not a computer game!