If you are receiving an error upon windows starting up in Windows 7, Error code: 0x80070002, after trying to uninstall Microsoft Security Essentials then follow the steps below to fix it.
Microsoft Security Essentials
First you will want to download and run the Microsoft Fix it tool from here: http://go.microsoft.com/?linkid=9775235
In our instance, the Fix it tool doesn’t clean/fix everything and we still need to delete a certain registry entry. So go to the start menu and launch “Regedit.”
Now browse to the following location. One of the folders under the “Uninstall” folder will contain a Microsoft Security Essentials entry on the right hand side. Delete that one.
Reboot your computer, and hopefully the error is now gone.