Microsoft today made the latest version of its Vista operating system available for download, following its release to official testers last Friday.

Release Candidate 1 (RC1) is one of the last versions of the software to be made available before the final code is released as the Vista operating system later this year.

It will initially be available to manufacturers, before going on sale to the general public in January.

About five million people joined Microsoft’s Vista Customer Preview Program to download and test the first Beta to be released, and these members will be offered the download before anyone else.

The company said it will reopen registration in the coming days.

RC1 code should be more stable than the previous Beta, although testers can still expect to find bugs that need fixing. This version will also have better driver support for peripheral devices.

If using a version of Windows older than XP, users will need to back up all files first (good practice anyway) before loading it, as it overwrites the hard disk.

XP users can choose to perform either a clean installation or upgrade their OS.

Once installed, users cannot roll back to their previous installation.

Instead you’ll need to reinstall a fresh version of XP, or buy Vista once released.

Vista RC1 works until 1 June 2007.

Microsoft also released Vista pricing details today, confirming the prices accidentally published on Amazon last week.

Vista Home Basic costs $100 (£53) for an upgrade version, or $199 for the full package.

Home Premium costs $159 as an upgrade or $239 for the full package.

Vista Ultimate, which is aimed at business and high-end home users, costs $259 to upgrade or $399 as a full package.

The Premium and Ultimate editions also include Microsoft’s Windows Media Center software.

More details on the individual versions can be found on the Microsoft Vista website.