Some people say it’s hard to keep adware off your PC. If you use some common sense, however, it can be quite easy to tell which kinds of programs are likely to have adware and which aren’t.

The least likely programs to have adware are very technical, obscure ones – their userbases just wouldn’t stand for it. Adware is most often included in slickly-marketed programs that fulfil a common, everyday need, as these programs will be downloaded far more by non-technical users who are less likely to know about adware.

At the moment, by far the biggest sources of adware are peer-to-peer filesharing programs like Kazaa. These programs come bundled with adware in the installer, mainly because the companies distributing them are keen to have a revenue stream and aren’t too concerned about their reputation, as they generally produce no other kinds of software.

There is also a lot of software, however, that actually does very little, and is nothing more than a delivery mechanism for adware. Bonzi Buddy, Comet Cursor and Hotbar are all examples of this.

Bonzi Buddy is a fun-looking purple monkey, clearly targeted at children, that reads out ads using text-to-speech technology. Comet Cursor allows you to easily change your what your mouse pointer looks like (trivial for a program to do), and installs an ad toolbar and shortcuts to affiliates’ websites on your desktop. Most recently, Hotbar, and other programs like it, are enticing young users to install them with the promise of smileys (emoticons), and in return take over the web browser, installing toolbars, changing the default search engine, and more besides.

If you want to avoid adware, there are two simple rules to follow. First, anything that seems too good to be true probably is. Second, don’t download any free program that you see in a banner ad or a pop-up – if they’ve bought an ad, they’re planning to make money off you somehow, and it might be through adware.