It has been revealed that in Microsoft's new release of their Virtual Server 2005 product, they will support Linux running as a virtual machine for the first time.
Virtualisation software, such as MS Virtual Server, VMware and Xen allows multiple 'guest' virtual computers to run on one physical machine. It's useful for testing new software on multiple platforms and for spreading the load on overstreched servers.
It's been almost traditional that Microsoft's Virtual Server product only fully supported Windows as a guest operating system for Virtual Server, but it seems they are about to change that. This is probably a response to the growing dominance of VMware, which works on Windows and Linux physical machines and hosts both Windows and Linux 'guests'. VMware also released a beta of a free version of their server product, for Windows and Linux which can be downloaded here.
Microsoft also announced that Virtual Server will be built into their next server operating system, currently still codenamed Windows Longhorn Server (but will probably be called Windows Server 2007). This is also to rival VMware's free product.
This news comes just as the open source Xen virtualisation software is branching out to run on Windows platforms, as it currently only works on Linux (but is already built into SUSE Linux and Red Hat Enterprise Linux).