Support.Microsoft.com: How Microsoft Ensures Virus-Free Software [by Using Unix]

[ Thanks to junkyinny for this link.
]

“Release Insertion Into Manufacturing
Network
Microsoft takes several steps to ensure the software we ship is
virus-free. This article describes the product release and
manufacturing/duplication process. References to “media” include
both floppy disks and CD-ROM disks.”

“The master is read into a UNIX-based disk duplication system.
The system creates an exact disk image of the master, duplicating
the format and data. A duplicated masters is created from the
original read in image. This silver master is used by the Product
Group in their review, before they sign-off. The silver master is
not to be used in the Release to Manufacturing (RTM) process. The
golden master, delivered by the product group to the release group,
is the original image, and is released to manufacturing when the
final approvals are received from the product groups.”

“Duplication Process
Disks are duplicated on a variety of industrial strength,
quality focused systems. Most of these systems are UNIX-based. The
UNIX-based duplication systems used in manufacturing are impervious
to MS-DOS-based, Windows- based, and Macintosh-based viruses.
The few MS-DOS-based and Windows-based standalone duplication
systems do not allow MS-DOS-based operating systems to access the
duplication system. Virus protection systems used by these
MS-DOS-based and Windows-based duplication systems strictly govern
the duplication process, even when they are not running.”

Complete
Story