After I have download the avast! Free Antivirus, the system was unsecured. but when I pressed “fix now”, it does not do anything. what should I do? Thanks in advance. 
Try avast repair and reboot
For a repair of avast. Windows, Add Remove programs, select ‘avast! Anti-Virus,’ click the Change/Remove button from the pop-up window, scroll down to Repair, click next and follow.
Did it work ?
Can!!! THANK YOU SO MUCH!! 