Dell 545s has black screen

[la321]

My moms god son has been using my computer but an ago he called me in and my screen is black Dell black screen - YouTube how can i fix this? i don't have the installation disc because this was a computer that had windows vista when i bought it and a disc came with it to upgrade to windows 7 i can't go into advanced setting by pressing f8 i only can press f2 and f12 i pressed f12 and ran diagnostics a message appeared saying it couldn't find any problems with my system then asked to continue to check memory

 

[redheat2010]

You need to reinstall windows do you have widows vista cd?