I have a toshiba c655 and one day it just stop booting up. All I can get on it is a black screen with a cursor.

If you are getting throught the POST (power on self test), then to a blinking screen, it is most likely that your hard drive has failed.

To test the rest of your computer's components, get a CD that is bootable, such as an OS installation CD, or a Linux bootable, and put it into the CD rom and boot the computer. if it boots to the CD, then your computer is OK, and it is a problem with the hard drive.

If you have important data on that drive, sometimes even if the hard drive fails, you can still access it by removing the hard drive and plugging into another computer via a USB interface.

Thanks! Im not getting anything but the startup screen and then it goes to the black screen and cursor.

I tried that and I'm getting a error saying I don't have an OS

did you follow the advice on the link and correctly s burniong software that burns the .ISO file to disk ,and not just copy the iso file to the disk .

use a program like isoimage burn if you need to .
http://www.imgburn.com/

Thanks for everything I think is my hard drive. It's not running at all. The computer isn't reading the disk at all.

the idea of using the disk is to ruel out the hrddrive ,the disk will load linux into RAM ,so if its not loading its something else .like ram or motherboard .
remember when i refer to harddrive i mean the drive inside the computer /laptop

Oh okay! Yes I remember when you said that. I'll check my RAM.