A Defence notice leaked to Computerworld and signed by chief technology officer Matt Yannopoulos said Microsoft was scratched out during a review of the department's information architecture management server, desktop roadmap, and defence approved software list reports.

"The CTO has assessed these products and deemed they provide no significant business advantage for Defence," the notice states.

"In addition, implementing these products would require an investment in new and upgraded hardware and the chief information officer group is not in a position to undertake this investment at this time."

Instead Defence will bypass Vista and consider a roll out of the upcoming Windows 7 platform.

The department only finished its upgrade to XP in 2007, an operating system that was released to the public in 2001.