Please help me, I realize this problem when I attempted to install an unknown program, which could be the virus. After I did a full system scan, the anti virus told that the virus has changed several settings. How can I fix this problem?

Hi Dough-Us, I suggest you first try a free online virus scan on the following site: http://safety.live.com Meanwhile, if you need more help with virus-related issues, please contact Microsoft Product Support Services. For support within the United States and Canada, call toll-free (866) PCSAFETY (727-2338). For support outside the United States and Canada, visit the Product Support Services Web page (http://support.microsoft.com/?pr=SecurityHome ). After removing those potential malware or virus, you can check the following thread for solution regarding Security Center issue: security center service will not start http://social.technet.microsoft.com/forums/en-US/itprovistasecurity/thread/c3e600fc-d3d7-4d8a-9bc4-c1eb0398664c/ Hope this helps!Sean Zhu - MSFT

ok..... lets try this...open services,select security center and right click for its properties,logon as NT AUTHORITY\LocalService.no password required.now apply and start service. ok reply.