Alongside Ad-Aware the famous Spybot Search and Destroy is the other key player in the anti-spyware arena. For years these bits of software have been protecting uneducated computer users from malicious spyware, trojans and malware. The protection offered by Spybot is slightly inferior to Lavasoft's offering but it comes in at the same low low price of $0 and unlike Ad-aware, you don't have to pay to access the extra features of the software.

Several of these are worth noting, firstly, the immunisation feature. Ad-aware offers similar protection, but requires you to pay before it is accessible. It makes the software operate like a virus scanner, constantly active and searching through files as you go about your business, so you don't have to worry about scanning your system all the time. Spybot also offers users the ability to lock certain features of their browser, such as the start page or the control panel, which will stop spyware interfering by changing settings. Ever come back to your computer and discover your homepage is now www.notavirus.com? Never again!

The second nifty function it has is less related to spyware, but is cool nonetheless. It offers the ability to properly delete files. You're probably thinking "but I delete files all the time...don't I?" and of course you do, to a degree, but the way a hard drive works means that typically when you delete a file, it isn't gone at all, at least not until more information is written over it. Certain pieces of software can recover files after deletion, which could prove troublesome later on. If you have sensitive data (credit card numbers, passwords etc) that you really want to be sure are gone then Spybot offers a risk free way to remove them when you're done.

We also liked the program's "system startup" tab, which lists all the files that fire up when you start your machine. Over the course of a year, the average user builds up a huge amount of unnecessary software, most of which boots up at startup, and they simply don't know how to stop it. Spybot allows you to choose what programs activate when you boot up your PC. You'll be amazed by the difference after you remove five or six programs.

We found the interface to be a little clunky. The features mentioned above are all stashed away in the advanced tools tab, which we didn't even know existed until we sat down to really explore the software properly. The basic anti-spyware scanning is easy enough to access, but sorting through the more advanced functions can be cumbersome. It also doesn't look nearly as sleek as Ad-Aware, with a very utilitarian menu system, however there is the option to skin it, personalising it a little.

Our testing proved that, as with Ad-Aware, Spybot is not an all encompassing package. Each piece of software picked up a few things the others didn't. Overall we felt Spybot came in a close second to Ad-Aware in terms of broad protection, but the difference was fairly minimal. If you run them both together you'll be all but impervious to the new age of digital infections, and as both of them are basically free, you have no reason not to!