Google will also provide desktop versions in a small box that connects to a monitor, keyboard and mouse, but no availability date was given.

Users will be encouraged to back up data and settings to cloud-based services -- whether they be Google services or those from the likes of Box.net -- to ensure that applications and data are available from any device and allow users to upgrade computers without a cumbersome installation process.

"We really want to make it possible for users to store their important data in the cloud and access it anytime, anywhere," said Sundar Pichai, vice president of Chrome at Google.

The success of online services shows that many users do trust their data to the cloud. Whether enough will do so to replace 75% of Windows computers is a point that will probably be debated for quite some time.

But there are clear benefits. Google says the computers start up in seconds, resume from sleep mode almost instantly and have battery life of either 6.5 hours or eight hours. On a first use, it only takes a few minutes to set the computer up.