Microsoft is preparing an update to Windows XP that is intended to make the operating system more secure.
XP is getting a security makeover
Dubbed Service Pack 2 (SP2) the update will close some loopholes that virus writers and malicious hackers have exploited to infect or take over PCs.
The add-on for XP will also include extras that block pop-up ads by default and give users a clearer picture of how secure their system is.
The update is due to be finished and released by the end of the summer.
"The security environment has changed since the launch of XP in 2001," said Matt Pilla, senior product manager for Windows at Microsoft. "Not only have hackers become more sophisticated and exploits more sophisticated but people are more connected than ever."
This made outbreaks likely to spread fast and be hard to contain, he said.
CHANGES DUE IN SP2
Pop-up ads blocked
Revamped firewall on by default
Outlook Express, Internet Explorer and Windows Messenger warn about attachments
Origins of downloaded files logged
Web graphics in e-mail no longer loaded by default
Some spyware blocked
Users regularly reminded about Windows Updates
Security Centre brings together information about anti-virus, updates and firewall
Protection against buffer over-runs
Windows Messenger Service turned off by default
He said SP2 was an answer to many of these changes and would make Windows XP more resilient against some of the attacks that have made headlines over the past few years.
Microsoft has been working with chip makers AMD and Intel on ways to stop so-called buffer over-runs that can help an attacker take over a target PC.
Changes have also been made to the underlying Windows technologies that the Blaster worm exploited to spread so fast.
As well as these changes users of Windows XP that install SP2 will notice more visible differences.
For instance Internet Explorer has been given a blocker for pop-up ads that will be turned on by default.
Viruses like Bagle prey on Windows
Before now people irritated by pop-ups have had to resort to other browsers or applications to keep the ads at bay.
Also added to Internet Explorer are download watchers that stop "spyware" being trickled on to a PC via background downloads.
Internet Explorer, Outlook Express and Windows Messenger will also warn about attachments to messages or downloads to prevent viruses or other malicious programs being installed.
Outlook Express will no longer automatically download graphics for web-formatted messages to foil spammers trying to harvest live mail accounts.
The firewall for XP-using PCs will be turned on by default in SP2.
In addition, all programs will have to be given explicit permission to use the web. None will get default access.
Users will also be regularly reminded about Windows Update to keep their machine up to date and limit exposure to potentially damaging loopholes.
Information about the status of the firewall on a PC as well as its anti-virus software and how well updated software is will be collected in a new program called the Security Centre.
"This is a fundamentally different kind of service pack," said Mr Pilla, "it will make Windows more resilient and more manageable and the features within it more visible.
Although Mr Pilla could not say how big the finished update will be in megabytes he said that users will be able to get hold of it by several different means.
Those on broadband connections will be able to download it but it will also be possible to order it direct from Microsoft and perhaps pick it up in stores.