Computer giant Microsoft is dropping customer support for the estimated 70 million users of its Windows 98 and Windows ME software.
The company says users need to upgrade the ageing operating systems as they could expose themselves to online security risks.
The majority of people using the software will be running it on home computers as by now most large businesses have phased it out.
Microsoft's website will still offer help and advice for customers who continue using the software.
The problem comes if the user's present-day computer cannot cope with the upgrade.
An upgrade will cost around €450, and it may be that a whole new hard disc is also required - taking the cost much higher.
The firm says it wants users to upgrade to a more secure system, such as Windows XP, as soon as possible.
A Microsoft spokesman said the company had declared its software would have a lifespan of around 10 years because of fast-evolving technology.
PA