thanks for asking your problem on justanswer.com
may be its happening because of virus so please update your antivirus software by its latest defination and scan your system.and also go to start->run-> type here %temp% , then a window will open and delete all temporary internet files.
then let us try this
please go to start->run-> type here msconfig , then a window will open after that go to startup tab and then click on disable all button.
after that restart your system