First of all its no longer "micosoft antispywre" now its called "windows defender"

It was released yesterday, although when you update microsofts antispyware it does not show up in updates. You have to manually download and install this (you'll have to uninstall microsofts antispyware 1st)

More information is provided here :

Microsoft encourages all Windows AntiSpyware (Beta) users to download and install Windows Defender (Beta 2).