Scroll down this page there are 3 or 4 ways to correct this.
Please let us know which antivirus and firewall product you use....
This is your answer, this is the same website I use when this happens to me.
ON the PC I have that has this happen, it occurs when a Windows Update requires a reboot to finish installing and by coincidence Symantec AntiVirus also downloads an update before the reboot.
The easiest way to fix this is to restore to a prior restore point. Then manually download and install what ever critical Windows Updates you have available. Disable your antivirus before boot, reboot, then update your antivirus.
You need to start at step two...
2. To Boot into Safe Mode and Use the built-in Administrator account
NOTE: You may not need to enable the built-in Administrator account. If this was the only normal administrator account you had, then Safe Mode should automatically boot into the built-in Administrator account.
It’s not complicated, thankfully MS fixed most of the causes of this problem and you shouldn’t see it more than once or twice a year now.