Kerry Scott, IT director for ActionAid, faced with a migration to Windows 2000 or Linux, said the low implementation costs of Linux with a Gnome user interface compared favourably to Windows.
Microsoft offers large discounts to charities but this only saves on the initial purchase.
"There are large hidden costs with Microsoft with the need to buy anti-virus software," Scott said. "We are now seeing the cost of viruses in downloading and installing updates on each desktop.
"Most viruses are targeting Outlook and the message seems to be 'avoid Microsoft and avoid viruses'."
Scott admitted that Linux was not as easy to install as Windows, despite improvements by distributors such as RedHat and SuSe. He is also aware that the choice of software is primarily limited to Sun's open sourced Staroffice productivity suite rather than Microsoft Office, so no decision will be made until the end of this year when a plan will be submitted to ActionAid's chief technical officer.
Mark Simmons, a senior analyst at Bloor Research, said, "It's a good idea to take time to evaluate Linux and, if the user is happy, it should provide a cheaper and more resilient platform.
"Where viruses are concerned, Microsoft is the focus at the moment but it may only be a matter of time before Linux attracts attention. In its favour, Linux has a worldwide base of thousands of developers to build better firewalls and security protection."
ActionAid, which addresses problems associated with poverty in the Third World, has an estimated 300 desktops in the UK and more than 1,000 worldwide. Scott said many of its users are in the poorest countries where IT support is difficult to find whatever the operating system.
The pros and cons of Linux vs Microsoft