Vista has died, have to load drivers?

just on my mates mac, basically i had just installed Just Cause 2 on my computer, i played it a bit, then went to bed but left my computer running. the next day my mates came over and used my computer and he said 'ah, its really slow, gonna restart it' but he just turned the power off at the back of the computer, and we restarted it and it said 'safe mode, safe mode with command prompt, safe mode with networking, last known good configuration, start windows normally' we tried them all but nothing works, so i fished out my Medion startup disc thing, and i chose repair and it said 'load drivers..' but i couldn't find any, and i also noticed that my harddrive doesn't show up. i think my harddrive has died, but i want some smarter people than me to gimme an opinion and how i can fix it because i can't live without my precious computer.