Thanks for the reply Shane. The failure of my Windows Defender has happened in the month of November 2012, I have just now discovered this community is only now that I wrote my post. I’m sure the fault has occurred after using CCleaner, with the setting of the cancellation only of “Windows Defender Definition Updates *”.
The idea to re-install Windows Defender on Windows Vista is not feasible, I could only fully restore Windows Vista with the recovery CDs but that would mean the loss of about 3 years of WinVista Update and the need to reinstall all my software !!!
Under these conditions, I agree to remain without Windows Defender? What do you think?
(Sorry for may bad English !!!)