Hackers beat Microsoft's secure shield

Microsoft has spent more than a year preparing a huge security update to its Windows XP software in an attempt to keep hackers at bay.

Today it let home users download it for the first time - but within hours, hackers had found dozens of new security holes.

Security firm Secunia and German company Heise claimed the problems could lead to new viruses designed to attack the computers of those who download the update.

Some users found their mostused software did not work. Microsoft confirmed that there were "compatibility issues" with some software.