LifeHacker: Microsoft's next version of Security Essentials is actually a pretty great update from its already-great predecessor. Microsoft's option has always been adequate at finding new malware without definitions, but the addition of an heuristic engine bumps its power up quite a bit. It may be subject to a few more false positives, but you're much less likely to get hit with malware than ever before.
Maximum PC: After more than 12 years of service, Microsoft finally pulled the plug on Windows XP by ceasing to support the operating system last week. However, Microsoft did promise to keep doling out updates for its Microsoft Security Essentials (MSE) software, including the version that runs on XP, but in doing so, the Redmond outfit only made things worse. That's because the latest MSE update is causing some XP machines to freeze up and run slow.
Maximum PC: "Microsoft Security Essentials has done it again. For the second time since its inception, the free antivirus software from Microsoft finds itself without German security and antivirus research outfit AV-TEST’s seal of approval, having failed in the latest of the firm’s bimonthly certification tests."
Microsoft has released the an updated Antimalware Engine 1.1.7000.0 for its free security solution “Microsoft Security Essentials v2.1” for Windows 7, Windows Vista and Windows XP. In this regard, there are two installers (32bit and 64bit) are being made available at Download Center.