My E520 starts up with the normal blue bar at the bottom, the next screen that comes up is black blank with a flashing cursor and then it changes to the black screen with white text and after that it doesn't load anymore and stays frozen

Hi, I need help. Last year I had windows XP on my system but at the begining of the year my brother formated my computer and installed windows 7. It worked fine for a few months. But one time it was on sleep mode, after I resumed it, it was frozen so i manually restarted the computer by pressing the button. However after I restarted the computer, there was the usual dell loading bar screen, a blank black cursor screen and then the black and white screen with text on it like:

serial ATA AHCI Bios, Version iSrc 1.02.23 08012006

controller bus#00, Device 1F, Function #02: 03 Ports, 03 Devices

Port-00: hard disk, Samsung HD160JJ/P

(this drive is controlled by RAID BIOS)

AHCI BIOS installed

etc etc

then theres a cursor after this information and then it stops loading. Usually it would change and there would be the windows 7 start up loading screen. But now it just stops. What do i do? ive tried changing th settings in the begining and looking at F2 and f12 but nothing seems to happen. I only want to format my computer as a last option just incase i have any files on my computer that havent been backed up. Please HELP ME :(