Given the frequency with which we bleat on about good PC practice, you'd be forgiven for thinking we were paragons of IT virtue. Sadly, this isn't always the case - Diskeeper's discoveries on one of our hoary old review PCs came like a much-needed shout of 'take some of your own advice' Even today's vast hard drives are quickly filled with files and programs large and small, which leads to a drop in performance. Whether defragging addresses this is a point of debate, but the general consensus is that it does. If you want to defrag, Diskeeper is an excellent way to do so, despite the defrag tool already present in Windows.

It comes in many flavours - but we decided to test the Professional Premier Edition. After a rapid installation and registration, you're faced with a simple interface. Your PC's drives are displayed in the top pane. A single click tells Diskeeper to analyse one. Full marks for the user interface; clear, concise and extremely easy to navigate.

The results are displayed in a colour-coded bar chart so you know just how badly your PC needs defragmentation. In our case, this was badly, so we quickly hit Defragment. You can work while this process churns on, but you'll find some programs run more slowly. Once you're nicely defragged, you can set up Frag Shield to offset future problems. What's more, you can schedule regular boot-time defrags and enable the 'Set it and forget it' mode.

And the results? Well, our 30GB hard disk was virtually full and totally miserable before we defragged - and slightly less stuffed but far perkier afterwards. This program is easy to use, has plenty of useful functionality and does what it's supposed to. Whether you're prepared to pay for this when Windows has a (limited) built-in defrag tool will depend on your circumstances, but there are plenty of versions to choose from.