From today home users will be able to get hold of Microsoft's long-awaited update for Windows XP.
The XP update conflicts with some games
The version of the SP2 security update for the Home Edition of XP has become available via its auto-update service.
However, users of XP Professional Edition must wait until 25 August to get a version intended for them.
Users who prefer to get a CD of the key update may have to wait a few weeks because the software was only recently released to disc manufacturers.
With the SP2 update, Microsoft is hoping to make it much more difficult for virus writers and malicious hackers to compromise the operating system.
As well as making changes to the innards of XP to make it more robust, SP2 also lets users manage anti-virus software, firewall and updates from one place.
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
The version of SP2 for Microsoft's corporate, rather than individual, customers was released earlier this month.
Today it is the turn of users of the home edition.
A Microsoft spokeswoman said the software should start making its way on to users' machines via the auto-update service from today.
Later this month it intends to let people download it for themselves.
Users can order it on CD but the spokeswoman said that because the update was only released to disc-pressing plants on 6 August it might take time to turn up.
The last group of users to get hold of the update will be those using the Professional edition of XP.
Early reports from Microsoft and many other places suggest that SP2 installations will not be glitch free.
Microsoft has produced a list of more than 50 programs that stop working properly when SP2 is installed.
Many of the programs affected are made by Microsoft itself. A lot of business users of Windows are delaying the installation of SP2 to complete testing and ensure it causes as few problems as possible.