My computer was running fine for ages but i tried turning it on and it started normally until i got a choiche of normal,logged,safe-mode or step by step. i've tried all of them but they just take me to a black screen with a flashing white line in the top left. I've tried pressing buttons, with no effect, and i've left it for over an hour. Please help...

You give us absolutely no information about your system and ask for help...do you expect an answer that'll do you any good? What is your system or motherboard; exactly? What operating system; XP, Win98, other? Did you do anything or anything happen just before this occured? Any error messages? Did you try the safe mode, last good configuration, normal etc. and just wait for awhile? This is no time to get frustrated and in a hurry. Or have you been waiting for something to happen for an hour? Gotta remember that none of us are sitting next to you and looking over your shoulder. Skip