Goes into f8 mode but nothing shows up except little underscore

Hello, i have a latitude E5510, it goes through the loading screen where it says DEll but then it goes into f8 mode but nothing shows up except a little underscore flashing in the to left corner, i don't know if i have tried everything but the things i have tried hasn't seemed to work, i dont want to do anything that will remove everything on the computer as i have done it before this happened. please help