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Microsoft this week renamed its antispyware software from Windows AntiSpyware to Windows Defender, which may be more appropriate for a combined spyware/virus defense solution, industry observers said. The company -- despite not setting a firm date for the next build and release of the security software -- did stress that the software will be aimed at more than spyware.
You said nobody has seen the Microsoft Anti-virus software, but it is available in beta testing. It is part of Microsoft's Windows OneCare program. I am currently testing OneCare now and it seems to work and is updated regularly. Maybe many aren't beta testing OneCare but you can sign up for it.