So just to re-confirm
Each time you start Windows you are then opeing Task Manager and running Explorer? To see the Desktop and everything
And everything has been turned off that can be
No Virus\Malware present
Gina values in registry checked, and possibly re-typed over the top (just in case of blank spaces or something)
Windows Repair done
Safe mode, I can't remember what's happening??
ok try this
Start->Run-> sfc /scannow (best to copy and paste this into run)