Startup problem

Hello,
My hp laptop just shut down while I was using it and now it shows the windows starting but then it goes to a black screen with nothing but a blinking underscore in the top left corner ! I really need this laptop for school work. What happened? Can it be fixed? And if so what can I do ?! Please help! Oh and I tried pressing f8 or f12 an stuff nothing worked except f2 and that only says startup check on the bottom then goes to a page with system info
Startup test run in test system tuneup hard disk test memory test batt. Test error log and exit. I don't know much about comps. So I have no clue what to do , please help !