To prevent confusion on the other thread that Stocker started about Windows defender I thought it might be best to start another one. My error pop up seems to be different than the one he was receiving. Here is the pop up I get on power up.

Application failed to initialize: 0x800106ba A problem caused Windows Defender service to stop. To start the service restart you computer or search help and support on how to start the service manually

I think many of the issues involve Windows Defender changed version. Beta 2 expired on December 31. Everywhere I have read,
1) start, control panel, add or remove programs, Windows Defender, change,
update

2) apply all critical security patches via WindowsUpdate--particularly, make
sure that the Windows Installer 3.1 is installed.

Or just unistall it, make sure you have all the appropriate/latest windows updates, especially Installer 3.1, then reinstall the latest version.

What happens if you uninstall Windows Defender (using Add/Remove programs in the Control Panel)? You would need to remove, then add it again.

I'm on the road now so I'll have to try when I get back home. Do I really need W Defenders?

I like it, especially for the price. It doesn't seem to burden the system anymore than any other full time running spam stopper/blocker. It is a lot less cumbersome than the ones I have seen from Symantic and McAfee.

Could you live without it, yes, but with the way so may things are going on virus/trojan/spam...etc developments, I definitely think its becoming a necessity as much a the AV.

Thanks guys, I uninstalled Windows Defender and reloaded it from the Microsoft site and these issues have ended. Ironically I never knew I had Windows Defender until the problem started....:crazy: