When you create a PowerPoint presentation, can you honestly say that you are sourcing and downloading images from a trusted source? Many of us have the luxury of being able to source logos, charts or images from a central library created for use within our own company, but sometimes it's crucial to find a visual reference from the wider world and that's when the internet is an unrivalled tool.

As search engines have become more sophisticated, there is now a wealth of knowledge available to take us out of the confines of the company slide library and our own digital album. Few of us give a second thought to using the internet for additional research. It's easy to track down and locate even the most obscure information, facts and figures - all of which adds a bit more punch to a presentation. But it's worth thinking about how to search and download images legally and without infringing the laws of copyright.

The ease of downloading from the internet has led people to believe that if something is on a website then it's free for anyone to use. Not only is this misconception untrue, it's also very dangerous.

If you do decide to widen your search and embark on trawling the net for images, there are two things you should take into account before you begin: one is permission and the other is cost. These two search parameters will then determine where you should fish for your bounty.

Reputable stock libraries exist in abundance and it's easy to search online and negotiate the use of anything from images of Aberdeen to Zanzibar Island. Libraries will help you through the maze of sourcing, costing and buying the use of high quality images for your presentation. Although cost is usually a downside to purchasing from a picture library, there is the option of choosing royalty-free over rights'-managed images. Royalty-free images do not ensure exclusive rights to use, but now often change hands for less than £1. As well as photo libraries, many micro-stock agencies have sprung up which can supply huge numbers of images at low a cost.

Some websites promoting the use of stock photography use sophisticated technology to trace the illegal download and use of their images. To be safe, it's best to assume all images are protected by copyright unless you have written permission to use them.

If you do search and source from a 'free' source, you must ask yourself if the images you are using are of good enough quality? The priority for a cheap stock photographer these days could be said to be the production of quantity and not necessarily always quality.

Once you have sourced and been granted permission to use the image, you will also have to adhere to any usage agreement. Do you need to credit the image in a certain way? And think about the restrictions to use the image - you might not be able to edit or amend how the image looks. The clever use of a picture editing program could create a bandage over the arm of the Venus de Milo, for example, and help produce a fantastic advertising campaign for medical supplies - but is it legal to do so?

Images are covered by the copyright law of the country in which they were generated, but they will be automatically protected in most other countries. Downloading images from the internet can confuse the issue, because it is sometimes unclear where the request came from and where the material is stored. However the penalties for infringing the rights of material available in digital form are very clear. If you remove any technical protection measures associated with the digital content or remove any rights information, this will now constitute an infringement of copyright and may be subject to criminal proceedings.

Even logos are covered by copyright laws - so don't reproduce anything unless you are certain you have permission to do so.

Social networking sites give access to a huge array of subject matter, and a new standard licensing system has emerged designed specifically for digital content on the internet, called Creative Commons. This enables people to license their photos in the way they want to. But just because an image is published on such a site does not mean that you can use it without obtaining permission. Even if you think that the Creative Commons licensing system is protecting you when you use a social networking site to source images, it might not. Be careful to evaluate the images you find. It is not uncommon for people to upload images that are not their own and make them available under Creative Commons licenses.

And remember the owner of the work may not hold the rights to reproduce. A fine art painting, for example, could be on display in your office but copyright to reproduce may still lie with the artist.

There's also the problem of using an image you have downloaded from an unofficial site - the quality will not usually be very high and can give your presentation a look of being cobbled together with substandard images. And while copyright isn't the only thing to worry about when putting a PowerPoint presentation online, it's worth, for example, considering how it will be viewed when using different browsers.

There are exceptions to copyright rules. For example, images used in an educational presentation can be sourced from sites which deal specifically with use in schools or colleges and have copyright clearance.

Then there's always clip art - and there are many free clip art websites online. However legal business use for free clip art images isn't easy to pinpoint since the original source is obscure, so free clip art images aren't recommended for professional use. Just as with photography, before using clip art, make sure the image matches the use you have planned. Read the license agreement and examine all legal limitations before you publish the image.

There are many other categories which are also protected by copyright. These include: literary, dramatic and artistic works, films, sound recordings, broadcasts, dramatic works and typographic works. Think about restrictions for animation and sound, too.

If you are adding music to your presentation, remember that this is also covered by the laws of copyright. And it's a good idea to check if both the music and words need clearance as sometimes music has been matched to words written by a different composer at a completely different time.