How can you tell when the motherboad is gone.

Hello,
I have an Inspiron E 1505. I have had it for about 5 years, and was crazy about my laptop. It shut down one day and I couldn't get it to come back on. A day or so later it came back on, but you could see little fine lines in the screen that moved whenever I moved the mouse.
So it stayed on for a while and then it shut off again, but this time it gave me a blue screen that said the system was halted, contact your hardware subscriber. Sometimes I can get it to come on and will even let me go the internet,but it will only stay on for a little while.
Sometimes when I turn on the power it does a repair and it may come on and sometimes it gives me that blue screen.Sometimes it will come on and the screen will be black, but I can hear it turn on.
What can this be? PLEASE HELP!!!!