Dell Desktop GX 620 Boot Help

My computer won't boot. Here are the symptoms:

1) the boot goes thru the 1,2, and 3 lights for booting. But it doesn't make it to the 4 light.
2) and underline cursor continuously in the left hand corner of the monitor display

Are we talking motherboard here?

Thanks for the help guys.

Scott

 

You'll need to explain because I have no idea what that means.

On the back of the computer (and sometimes in the front) are diagnostic lights.

Go here to read what the lights are telling you
http://phubner.eng.ua.edu/Files/Optiplex GX620/tools00.htm#wp1114558

 

I believe the diagnostic lights are in front. The 1, 2, and 3 lights light up, but not the fourth. Does that help at all? Thanks

 

Sorry, the link you provided was helpful. I just moved, so a cable might have gotten disconnect during. Would you say if all the cables are attached and copasetic, are we talking about a failure that's unrecoverable?

 

If 1, 2 and 3 are green and light 4 is off, the diagnosis is this

Have you opened the computer and made sure everything is securely attached?
Apparently you get no message on your screen just an underline that blinks. Is that correct?

 

Yes, opened comp and the connections and they seem wired good. Yes, no message showing up on screen. I'm thinking of replacing it with a Dell 580. If I do, is it fairly easy for the retailer to transfer my existing to the new comp? I know Macs are easy to do.