Windows Live OneCare Beta (v2.5)
Since a few weeks a new Windows Live OneCare v2.5 BETA has been released. If you're interested then click here and fill out a short survey at Microsoft Connect.
Of course you'll have to uninstall the previous version first, or any other antivirus program you may have installed. For more information check the Windows Live OneCare at Microsoft Connect. Support forums and where you can get a lot of good information is at Windows Live OneCare Support Forums.
More details at: The Windows Experience Blog