Pleeeease  help me. My Dell Inspiron 2000 started showing 'unmountable_boot_volume' on a blue screen everytime i try to switch it on. Its totally out of the blue and ive got stuff onit that i need for my finals at uni. I cant get past the screen and have tried Ctrl and F12 but it keeps saying Loading PBR for discriptor  3 ...done

No loader

 

I never get any further. Please explain in dummy terms (button by button and screen by screen) wot to do cause i dont understand all these computer terms. Im computer iliterate. Please help me, my degree depends on this!!!!!!