Security was a top priority for Microsoft, company chairman and chief software architect Bill Gates said this week as he announced free spyware and malware removal tools, upcoming antivirus software, a revamped Internet Explorer browser and server security updates.

Speaking to thousands of security experts and business customers at the RSA Data Security Conference, Mr Gates said that security research now received a third of the company's $6 billion annual research and development budget.

"Our primary goal is to improve security and safety for all our customers through a balance of technology innovation, guidance and industry leadership," he said.

With security now a major worry for customers, industry observers see the participation of Mr Gates as clear evidence of the company's growing concern to address both security issues and public perceptions of the company and bolster the image of its Windows operating system, which has flaws that are regularly exploited by attackers on the internet.

Mr Gates's keynote speech marks the second time in a row that he has opened the huge security conference, where for many years Microsoft, perceived as weak on product security, was a target of criticism and jokes.

In the past, Microsoft usually sent management figures at a lower level to give these presentations.

In his speech, Mr Gates confirmed speculation that the company would enter the antivirus software market by the end of this year with a product born out of its intended acquisition of antivirus company Sybari, which Microsoft announced last week.

Sybari has software for the corporate market that targets computer worms, spam and other types of online attacks.

The arrival of the software giant in the antivirus market will challenge the position of market leaders such as Symantec, whose chief executive, Mr John Thompson, also gave a keynote at Tuesday at RSA.

During his speech he noted that while he "applauded Microsoft's security initiatives" as "necessary", he also felt they were "not sufficient for large enterprises".

He added that Symantec, which focuses entirely on security products, was not distracted by also offering games and other products.

Microsoft is also to release a free program later this year that allows computer users to scan their systems for spyware and malware, and helps to prevent them from unwittingly downloading the troublesome programs.

The beta release of the program has been downloaded over six million times, and many users are using a feature that allows them to send a report about suspicious programs back to Microsoft, which in turn helps the company to further develop the tool to block more unwanted programs, Mr Gates said.

Spyware and malware are small, hidden programs that users often download with free software offered on the internet.

Once installed - a process that also often happens without the user realising it - the programs track what a user does on the computer and sends back the information to marketers (in the case of spyware).

Spyware can also slow down a PC's operations.

Malware can sabotage a computer system, take control of it for secret use by hackers, or send personal information such as passwords and account numbers back to the attackers.

Mr Gates also promised new security protections in a new release of Internet Explorer (IE), due out later in the year.

Holes in the IE browser have been a regular source of security breaches for computer users, and Microsoft has had to issue regular patches to repair flaws.

Security concerns are believed to be a major reason why a new free browser called Firefox has begun to pick up market share from Internet Explorer, the first time that usage of IE has slipped noticeably.

Mr Gates noted that 170 million people had downloaded Microsoft Service Pack 2, a set of programs and patches that are intended to up the security of operating system Windows XP.

He said the company would push to get 100 per cent of users to install the pack.

He said that he was confident that Microsoft would be able to "mitigate the security problems and let the advances of this digital infrastructure allow some fantastic things to happen".