Sun Microsystems has entered into a stock purchase agreement to acquire Innotek, a provider of open source virtualisation software.

Innotek's flagship VirtualBox offering will be used to extend Sun's existing xVM platform onto the desktop.

VirtualBox enables desktop or laptop PCs running the Windows, Linux, Mac or Solaris operating systems to run multiple operating systems side-by-side, switching between them with the click of the mouse.

"Innotek provides Sun with the perfect complement to our recently announced Sun xVM Server product," said Rich Green, executive vice president at Sun.

"VirtualBox is ideal for any laptop or desktop environment and will align perfectly with Sun's other developer focused assets such as GlassFish, OpenSolaris, OpenJDK and soon MySQL as well as a wide range of community open source projects."

VirtualBox is open source and can be downloaded without charge from virtualbox.org or openxvm.org.

The download is less than 20MB and is installed on any modern x86 architecture laptop or desktop system running Windows, Linux, Mac and Solaris operating systems.

The agreement to acquire Innotek follows Sun's announcement on 16 January of a definitive agreement to acquire MySQL, the world's most popular open source database.

The stock purchase agreement to acquire Innotek is subject to customary closing conditions and is expected to be completed during the third quarter of Sun's 2008 fiscal year.

The terms of the deal were not disclosed as the transaction is not material to Sun's earnings per share.