SilentStream is a water cooling system for your PC. For many people, the idea of introducing anything containing water inside the box of their PC may cause sweaty palms, but Global WIN has thought of this by pre-filling the system, so that in its simplest installation you don't have to add water to make it work.

The cooling block of the SilentStream clamps onto the top of your processor, in place of the heat sink and fan that you'd normally fit for air cooling. It uses an ingenious impeller to move the water around, which is driven from outside the sealed water system using a magnetic coupling.

There are two places you can fit the radiator block for SilentStream: inside or outside your PC's case. Either location requires fixing holes for an 80mm fan; these are pretty commonplace on modern cases, but check yours first.

The 'Quick' way of fixing the unit is to attach it to the rear of the case on the inside. Using this technique you can get the whole system running in five minutes or so, but you won't get the maximum cooling SilentStream can provide.

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Even so, you should expect to see an improvement of around 6 degrees Centigrade over the running temperature using a typical Pentium 4 air circulation fan, or around 3.5 degrees for an Athlon XP fan, based on the types supplied with retail-boxed processors.

You can improve this performance by removing the ventilated case section within the area enclosed by the 80mm fixing holes on the back of the case. This requires modification to the case, of course, and is probably best done if you're mounting SilentStream in a system you're building from scratch.

Even better cooling can be obtained by fitting the radiator block on the outside of the case, but the technical reader will have spotted a potential problem, in that the radiator block is too big to fit through a PCI slot back plate.

For this 'Professional' fitting, you need to remove some of the water pipes from SilentStream and drain the system before feeding them through a supplied back plate and reconnecting them to the radiator unit on the outside.

You then have to refill the cooling system and bleed it of any air, to ensure maximum cooling and minimum noise - air bubbles in the system can make it quite noisy. This installation is more fiddly than difficult, but is best reserved for those who like tinkering with motorbikes and suchlike.

With the radiator block fitted to the outside of the case, you can expect cooling figures of over 10 degrees Centigrade for a typical Pentium 4, or 8 degrees on an Athlon XP rig. What you have to decide is whether the cost is worth these extra degrees.

Note that the 'Silent' part of the name is a bit misleading; although this is a little quieter than some conventional cooling fans, it's really the extra cooling capability that you're paying for, not noise reduction.

Whether you go for the 'Quick' or 'Professional' installation, SilentStream is a well-made and intelligently designed water cooling system, ideal for those who demand maximum cooling in hard-working or over-clocked PCs.