Hey what's up guys, I have a hp pavilion 7915... But the other day I ran into a huge problem... Now every time I turn on my computer.. It does nothing but just show a blank screen and say "Operating System Not Found" ... It does not go any further then this.. it doesn't even log into my account on the computer.. So being able to browse on the computer is a no go.. It does not startup my computer.. Right when I turn the computer on it goes straight up Operating System Not Found... I wanna just restore everything to the factory shipped.. I tried pressing f1 and f11 but nothing in the menu leads to being able to do so.. I don't have the cd-rom it came with.. Any help or ideas on what I can do to get this bad boy running again?