my computer will boot up fine, but it dies once it tries to get to the log-in screen. sometimes it'll show the log-in screen [but when i try to log-in, it freezes], and sometimes it'll be frozen the blue screen right before the log-in screen shows up.

i can [and am] working in safe mode [directory services]. that's the only way i know how to get on my computer.

i asked some friends and they said my hdd is fried, and that i should do a full system back-up and wipe my computer. if that's the case, how do i back up my computer, and how do i wipe my computer?

if that's not the case, what's wrong with my computer, and how can i fix it?