A senior Microsoft executive has promised that its new operating system will be more secure than ever.

Jean-Philippe Courtois, president of Microsoft International, said that beefing-up security was one reason behind delays to Windows Vista.

Microsoft has been criticised for flaws in previous systems that left users vulnerable to attacks by hackers.

Mr Courtois said Microsoft had done "tons of work to make Vista a fantastic experience when it comes to security".

The firm had originally aimed to launch Vista - the first major update since Windows XP was introduced five years ago - in the second half of 2006.

The new operating system will now be released to business customers "within the next few weeks" and to consumers early next year, he said.

Secure steps

Speaking in Barcelona at the European Technology Round Table Mr Courtois, the most senior Microsoft executive outside of the US, said that Windows Vista was the continuation of an ongoing effort by Microsoft to improve security across its software line-up.

"In the last 18 months, the number of vulnerabilities [in Windows' software] has been much lower," he said.

At the heart of the system will be the new Windows Security Centre which will show consumers any holes in their defences.

Vista will also feature new encryption technology designed to protect the data on a computer.

"Even if your laptop is stolen, nobody will be able to use it because it will be fully encrypted," he said.

But Jean-Philippe Courtois said users had to play their part in making computers more secure.

"You've got to make sure that your firewall is on, that you've got anti-virus protection on your PC, you've got to understand what not to do on the internet," he said. "It's just like protecting your own home."

This week the BBC set up a so-called "honeypot" computer running Windows XP without protection. The PC came under attack every 15 minutes.

But not everybody in the security software world is happy about Microsoft's plans for Vista.

Symantec, which makes Norton anti-virus software, is among many security firms warning that Vista appears designed to shut out security products made by outside firms.

However, what is clear is that the long-awaited arrival of the new operating system will be a crucial weapon in Microsoft's battle to retain its dominant position at a time when firms like Google are mounting a serious challenge.

"The launch of Windows Vista is certainly one of the defining moments of the company," admitted Jean-Philippe Courtois.