Windows Defender Beta 2 (previously knows as Microsoft Antispyware) has been released to the public
Please!! read the Release Notes and the FAQ before using the download link:
Windows Defender Beta 2
Note: Beta 2 of Windows Defender is not affected by the Symantec Antivirus (Corporate Version) and Symantec Client Security misdetection from a few days ago. Only those running Symantec Antivirus (SAV) Corporate Edition versions 7, 8, 9 or 10 or Symantec Client Security (SCS) versions 1, 2 or 3 in combination with Windows AntiSpyware Beta 1 were affected. Definition update 5805 was affected.. 5807 fixed the problem. Symantec Product Support Services have released a free tool to fix the problems caused by the misdetection.
The Windows Defender Systray icon (a little castle) will only appear while the programme is active. I'll update this blog entry this evening with instructions on how to check that the programme is running in the icon's absence.. out of time now... lunch break is over ;o)
Edit: The services you should check to make sure that Windows Defender is running are MSAScui.exe and MsMpEng.exe. To check running services, right click in the systray area and select "Task Manager".
Make sure you have automatic updates enabled - that's the quickest way to get the latest definitions.