Microsoft has officially launched the latest version of its PC operating system, Windows 8.

At its dedicated event in New York, where Pocket-lint was in attendance, the company lifted the lid on both the desktop and laptop versions of the software and Windows RT, the version of the OS specifically designed for touchscreen tablets and devices.

Steven Sinofsky, president of Windows and Windows Live Divisions at Microsoft, described Windows 8 as "simply the best release of Windows ever".

He said: "We built Windows 8 on the foundation of Windows 7. But made it much, much better."

Read: Pocket-lint's extensive Windows 8 review

Microsoft said it had spent 1.24 billion hours of pre-release testing in more than 190 countries, thanks partly to builds being installed on over 16 million PCs during the beta and testing periods.

Available from tomorrow (Friday 26 October) for download from the dedicated Windows Stores in each country, the Windows 8 Pro upgrade starts at $39.99 in the US, £24.99 in the UK. These are reduced prices that will remain in effect until 31 January 2013 and are limited to five upgrade licences per customer. The software can upgrade from Windows XP SP3, Vista and Windows 7.

If you don't want to download the upgrades, you can have physical media versions sent to you. This does come at a premium, however, costing from $69.99 in the US and £49.99 in the UK.

The new operating system will also be available in certain retailers including John Lewis and Currys & PC World, which is holding a midnight opening launch event at its Tottenham Court Road, London, flagship store tonight. UK consumers will be able to get it first there.