Windows Vista is "dramatically more secure than any other operating system released", Microsoft founder Bill Gates has told BBC News.
Mr Gates said the security features in the new operating system were reason enough to upgrade from Windows XP.
Microsoft launched Vista in London, with more than 100m computers predicted to be using it within 12 months.
Mr Gates also defended the pricing of Vista, which is twice as expensive in Europe compared to the US.
The technology leader called the launch a "big day" that would bring a new digital workstyle and lifestyle.
The new operating system (OS) boasts an improved interface and security tools.
Mr Gates said security in Vista would mean it would be "much, much harder" for malicious hackers to attack computers running the operating system.
"For anybody worried about safety, whether it is phishing or malware or parental control type issues, Vista brings that to a whole new level of capability," he added.
Security analysts have praised the improved tools in Vista but many feel that holes in the operating system eventually will be exposed and that Microsoft will continue to need to update it through online patches.
WHAT IS AN OPERATING SYSTEM?
It is the program which manages the hardware and software resources on a computer.
It also forms a platform on top of which other programs can run.
Microsoft will come under fire if Vista proves to be the popular target of malicious hackers exploiting flaws, said David Mitchell, the software practice leader at analysts Ovum.
"It's crucial for corporate reputation and revenue that Vista proves more secure and stable than XP," he said.
Not all PCs will be able to run Vista - Microsoft recommends machines have at least 512Mb of RAM, a 800Mhz processor and 15Gb of hard disk space.
Microsoft has pledged to continue support for XP users until 2011.
The company launched Vista for business users two months ago. Now Vista has been released to consumers, who can buy four home versions.
There is also a stripped down version of the OS, Vista Starter, which is aimed at customers in developing countries. It will be available in 70 languages and will run on slower and older PCs.
VISTA PC SPECIFICATIONS
DirectX9 capable graphics processor
128Mb graphics memory
40Gb hard drive
But Microsoft could face a backlash from consumers over its pricing plans - with the cost of Vista versions in the US roughly half the price of equivalent versions in the UK.
Prices for the OS in the UK range from about £100 for an upgrade version of the Basic package to £249 for a copy of the upgrade to the Ultimate version of Vista.
In the US prices start from $100 (£52) for an upgrade of Vista Home basic to $249 (£127) for the equivalent Ultimate version.
Mr Gates defended Microsoft's pricing plans: "We try to keep our prices largely in line from country to country... but with price you do generally get some things that get a bit out of alignment as currencies go up and down.
"Our goal across our product line is to largely have a global way of looking at things."
Mr Mitchell said there was pent up consumer demand for Vista.
VISTA HOME VERSIONS
Home Basic - improved search and security but no Aero interface (pictured)
Home Premium - As above but with Aero, Media Center options, back-up tools, DVD burning software
Vista Ultimate - All home and business features, plus a series of downloadable Ultimate Extras
"In the consumer space there has not been any new release of a Windows operating system for five years," he said.
Ovum predicts that 15% of XP machines will be running Vista by the end of 2007.
"Part of the appetite is 'something new for something new's sake'," said Mr Mitchell.
Mr Mitchell predicted that the new graphical interface, called Aero, improved desktop search tools and a promise of more robust security would appeal to many users.
But he predicted some consumers could be confused by the minimum specifications for PCs to run Vista and by the different versions on sale.
Users can visit the Microsoft website to check if their hardware will run Vista and some new machines are being labelled Vista Capable or Premier Vista Ready, for those PCs with higher specifications.
"There's been an attempt to demystify what the minimum specifications are," said Mr Mitchell.
"Undoubtedly some people - as in any industry - won't read the instructions."
In his interview with the BBC Mr Gates also predicted that school children would be using tablet PCs rather than text books in 10 years time.
"We will have an inexpensive tablet-like device that lets the teachers customise things.
"Hopefully the cost of that isn't much more than textbooks have been so that's a big change."
He also welcomed the arrival of Apple's iPhone into the market calling it "a great new entrant"
"What we are seeing for all these products is that software is increasingly important. If you look at a phone of five years ago it was really about the hardware only.
"But now as you are browsing and managing your calendar and having lots of music or photos, the software is the thing that counts and there are very few companies to do great software."
Microsoft produces software which runs on millions of mobile phones and portable devices.
He added: "We enjoy having them [Apple] in the business."