Operating system not found error windows 7?

if it says "operating system not found" it means that you probably formatted your hard disk and it doesn't have windows 7 installed anymore, or you deleted the files that make windows start. if your computer comes with a windows 7 installation disc, put it in your cd/dvd drive and boot the computer from it, then select the recovery option. if it doesn't, it probably has a built-in recovery environment. if it does, start your computer, when it shows the manufacturers logo, press the button that opens the menu and it will have a recovery option.