My Samsung NP350E7C-A01US has windows 8 is not starting up but only Samsung logo and stuck there unless I use F2, then F9, then F10 and then comes up but is super slow and not useable. I did not recently download any updates. I use Avast free virus and Anti Malware free and CCleaner. When I attempted to open system restore it would not respond and locked up and after 10 minutes I ended it using task manager which was also slow to open and work. I now have it up and need to test to see what is cause. Please help.