The world as we knew it changed on Wednesday.

That was the day that the ever-changeable Sun, once Microsoft's most scathing critic pledged to its utter destruction, ate a royal serving of crow and signed up as a Windows Server OEM for the purpose of moving more margin-thin industry-standard boxes.

It will be paying Microsoft for the privilege of pre-installing the operating system on any and all of its so-called x64 Intel and AMD systems, including its new high-end Galaxies, for the first time because, it said, all of its customers run Microsoft.

Windows Server 2003 should be available on the first Sun systems in 90 days (see http://www.sun.com/software/windows/ for the rollout schedule). Sun has previously only installed Windows if a customer had a license with Microsoft.

There was no mention of the eventual Windows Server 2008.

The twosome envision the gear being be used with Microsoft Virtual Server, SQL Server and Exchange Server though Sun won't pre-install that stuff and will leave it to the channel.

The pair is supposed to ensure that Solaris runs well as a guest on Microsoft's virtualization technologies and that Windows Server runs well as a guest on Sun's virtualization technologies.

Sun conceded that Solaris' built-in virtualization doesn't solve everybody's needs.

The companies are supposed to work together on a support process for customers who are using the virtualization solutions.

Microsoft's Mediaroom IPTV and multimedia platform are particularly important to Sun since AT&T U-verse digital TV has chosen Sun for one of world's largest deployments of the Mediaroom platform, which includes server and client software.

The expanded alliance has Microsoft and Sun building an Interoperability Center on Microsoft's Redmond campus where customers can see Sun systems and proofs-of-concept running and benchmarked. The widgetry is supposed to include joint Sun/Microsoft solutions in database, e-mail and messaging, virtualization and Remote Desktop Protocol (RDP) support in Sun Ray thin clients.

Sun systems are currently showcased and customer tested in Microsoft's Enterprise Engineering Center.

The deal is supposed to build on the pair's little-used April 2004 cooperation agreement arranged when Microsoft agreed to pay Sun close to $1.6 billion to settle antitrust claims.

Last month, Sun arranged for rival IBM to install x86 Solaris on the machines it sells.