Microsoft is hoping that Windows XP Service Pack 2 will make life more difficult for hackers and spammers.
The software is currently at 'candidate one' release stage, as Microsoft decides on the user interface and finalises some of the latest measures to block virus propagation.
The update will go through a second stage of checking before being released in July or early August.
Richard Edwards, research analyst at Butler Group, suggested that home users will be the biggest beneficiaries.
"Proportionally that's where XP is at its widest deployment," he explained.
"This is a serious improvement in the user interface and is happy news for those most hard pressed in technical support: the techies who get called by friends and family to sort out their home PCs."
A new Attachment Execution Services module that analyses files sent into the PC will make it harder for viruses to spread through Outlook, Messenger and Internet Explorer.
A file contents history is displayed in a dialogue box before the user can open any attachments, and digital certificates can also be checked.
It is hoped that the improvements will protect against traditional Trojans and viruses currently being used by hackers and spammers.
Software to deal with viruses sent in encrypted Zip files is also being developed. Such files are opened in a secure 'sandbox' and scanned for viruses before being allowed further.
David Overton, a technical Windows specialist at Microsoft, said: "It instigates antivirus software checks on file contents of the Zip folders so that the very latest worms like Bagel cannot get onto systems."
Internet Explorer has new features, most noticeably the turning on by default of existing pop-up blocking software.
The browser will also block pop ups under windows, windows that are bigger than the computer screen and frameless windows. Macromedia ads can also be blocked.
All of these settings can be altered, either by script or from two new icons in the Control Panel for the firewall and Security Centre.
Although the service pack will be available as a download, Dixons Stores Group and others will be carrying free CDs as it weighs in at around 80MB.
Customers can also apply direct to Microsoft for a copy on CD but may have to pay postage and packing.
Some parts of Atacama have not received rainfall for 500 years - but a sudden deluge of water upset the Desert's delicate biological balance
Spitzer Space Telescope could not spot Oumuamua, suggesting that it is actually pretty small
Greenland crater one of the 25 largest impact craters on Earth
This long-sought progenitor star was identified in an image captured by Hubble in 2007