I can access my Security Center. It seems normal.
I tried to list restore point, when I clicked next button ( step 3), the message pop up said system restore has been turned off. I went to check control panel->system->systemrestore tap, the "Turn off systemrestore" check box is checked! ( but yesterday, everytime I restart computer, the check box is not checked. ), I uncheck it. and list the restore point, there is only one item, dated today "1:49pm system checkpoint", which is about the time when I unchecked that check box.
I amgoing to try to check that checkbox and restart computer and see what happens.