The Problem:-When I boot my system I find the security center bubble telling me that my NAV is not started but within 20 secs. after NAV has loaded the bubble disappears.Why is it so?
That is normal. The Security Center is monitoring before your antivirus is completely running, thus the bubble disappears once it is running.
Still if you don't want to see that warning bubble then:-Open Control Panel,Click Security Center and click on "Change the way Security Alerts me" at the left side of the window and then uncheck "Virus Protection". Warning though... you will not be alerted if your virus protection actually doesn't start.
Manage Your Computer's Security Settings in One Place