If your Windows security settings were changed by some software, script or a virus there is a way to reset it back to defaults. Different security changes might have negative influence on PC performance. However it is hard to clarify if security changes led to certain PC problem.
Note that this technique does not restore all security settings that are applied when you install Windows. Also this technique do not apply to Windows XP Home Edition, or Windows Vista Home Basic and Home Premium editions.
Steps to restore security settings:
1. Open Command Prompt:
In Windows XP:
Click Start, click Run, type cmd, and then press ENTER.
In Windows Vista:
Click Start and then type cmd in the Start Search box.
In the results area, right-click cmd.exe, and then click Run as administrator.
2. In the command prompt do the following:
In Windows XP:
type the following command, and then press ENTER:
secedit /configure /cfg %windir%\repair\secsetup.inf /db secsetup.sdb /verbose
In Windows Vista:
type the following command, and then press ENTER:
secedit /configure /cfg %windir%\inf\defltbase.inf /db defltbase.sdb /verbose
You receive a "Task is completed" message and a warning message that something could not be done. You can safely ignore this message.
Now your system security settings have default values.