Microsoft Security Essentials Vanished

I noticed Monday evening that MSE was gone, poof from my system. At first I feared malware that had disabled it but I discovered an update had failed early Monday morning. When I searched for that KB number I discovered that some users are having problems with the Windows Update package.

If you use MSE, Check to see if it is still running on your system; if not, check your update history.

Fortunately the solution that worked for me was to download the MSE package from MS, reboot, and install. Before doing that I reactivated and updated Windows Defender. (What is the difference between Windows Defender and MSE?)

My error was as follows:

Microsoft Security Essentials Client Update Package - KB2544035

Installation date: ‎2011-‎08-‎01 03:01
Installation status: Failed
Error details: Code 80070643
Update type: Important
This package will update Microsoft Security Essentials client on the user's machine.

More information: (These links took me to the MSE home page.)
http://go.microsoft.com/fwlink/?LinkId=195462

Help and Support:
http://go.microsoft.com/fwlink/?LinkId=195463

It sounds strange, I have no problem with MSE, it is both running and updates the definitions smoothly.

Hello djl47 and welcome to Seven Forums.

Thanks for posting that information.

Windows Defender is software that helps protect your computer against pop-ups, slow performance, and security threats caused by spyware and other unwanted software by detecting and removing known spyware from your computer.

Source

Microsoft Security Essentials provides real-time protection for your home or small business PC that guards against viruses, spyware, and other malicious software.

Source

So, Defender is pretty much an anti-spyware product while MSE is a suite of anti-malware tools.