Windows users are being urged to download the latest security updates from Microsoft to fix critical flaws.
Windows is used in most of the world's home computers
The software giant has warned that three loopholes affecting Windows and Internet Explorer allow an attacker to take control of a personal computer.
Seven other updates have also been released to address less serious problems in its software.
Microsoft has been trying to improve the security of its software, releasing regular monthly security bulletins.
Microsoft first alerted the millions of Windows users that it was planning a bumper pack of patches last week.
"For all consumers we recommend that they have Automatic Updates enabled," said Stephen Toulouse from Microsoft's Security Response Center.
Windows 98, ME, 2000, XP, Server 2003
Windows Web Client Service
Windows Interactive Training
Windows Telnet Client
Microsoft ISA Server 2000
This is a feature in Windows that downloads the software patches automatically. Computer users can also get the fixes manually from Microsoft security website.
The most serious flaws affect Windows and Internet Explorer and could be exploited by a malicious hacker to take over a computer system.
The other patches affect Windows, the Exchange server system, services for the Unix operating system, Microsoft's Interactive Training software for Windows, and ISA server, a network firewall program.
Last month, Microsoft announced plans to offer its own anti-virus and security updates for home computers, called Windows OneCare.
The service would be on a yearly subscription basis, just like other anti-virus protection services.
It is being tested by the Microsoft employees before a trial release for the rest of the world later this year.
Although Microsoft already offers security features in its software for free, it recently bought anti-virus technology to help beef up security.