Users can download the software or buy it in a shop
Users worried about staying safe online will soon be able to get software to protect their home PC direct from Microsoft.
The software giant's first security product goes on sale in the US from 1 June and will become available in other countries over the next 12 months.
The product, dubbed OneCare, rolls anti-virus, anti-spyware and firewall programs into one package.
OneCare costs $49.95 (£26.50) to protect three computers for a year.
The OneCare package has been under development since mid-2003, and many Windows XP users have been testing early versions of it for Microsoft. The software is aimed at consumers and small businesses which currently have only the most basic protection against net-borne threats.
Microsoft said up to 70% of consumers either have no security software on their PC or have programs that are no longer updated.
As well as providing security programs, OneCare also includes back-up software that helps people recover important data in the event of problems. Those signed up to the service also get alerts about emerging threats and advice about what they need to do to counter them.
The software goes into shops and is available for download from 1 June.
Because Microsoft's Windows operating system is used on so many desktop PCs, it is by far the biggest target for net-based vandals and criminals.
Lax security on many home PCs, particularly those sitting on fast broadband links, has proved a bonanza for net criminals. Now it is estimated that 70% of junk e-mail or spam is routed via home computers hijacked through vulnerabilities in Windows.
The security failings of Windows has led to the creation of a huge industry that aims to make the operating system more secure. Microsoft's foray into security software pits it into competition with some companies such as Symantec, McAfee, Trend Micro and many others.
Both Symantec and McAfee are preparing all-in-one software packages that aim to do the same as OneCare.
Microsoft has said that, so far, it has no plans to build OneCare into its Windows XP operating system as it has with its net browser and media player. However it is likely that PC makers will offer the service as an extra when consumers buy a new machine.
The launch comes as security firms warn of the emergence of a trojan that poses as a security update from Microsoft - the latest in a long line of viruses that try this trick.