Microsoft chairman Bill Gates has officially launched Windows Vista and Office 2007 to the consumer market, two months after the software was released to business customers.

Vista comes with a new graphical user interface dubbed Aero, better multimedia support and enhanced security technology.

At the UK launch event at the British Library, Gates predicted that the software would be on a 100 million computers by the end of the year.

"This 'wow' thing is a great way of describing what we've got here," he told Associated Press. "There are chances for 'wows' all over the product."

Microsoft recommends machines have at least 512Mb of Ram, an 800MHz processor and 15GB of hard disk space to run the system.

However, to get the best results, a minimum specification of a 1GHz processor, 1Gb of Ram, 128Mb graphics memory and a 40GB hard drive is recommended.

Prices 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. This has angered some UK users since the prices are nearly double those paid by US consumers.

Nevertheless, with all major PC manufacturers preloading the software on new machines capable of handling it, take-up among consumers is expected to be high.

"HP has collaborated closely with Microsoft for more than five years to deliver the industry's broadest and most complete Windows Vista portfolio," said Shane Robison, executive vice president and chief strategy and technology officer at HP.