your are infected by conflicker or w32.downadup virus, try to check this link http://www.symantec.com/security_response/writeup.jsp?docid=2009-011316-0247-99, and disable the autorun in your computer, just google it how to disable the autorun, and if you shutdown your computer when you are not using it, then the settings of the virus is already save in your registry, please disable your system restore here how to http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2001012513122239?OpenDocument&src=sec_doc_nam before you scan your computer with the symantec removal tools