Dell 1545 screen problems

Hello,

I have a dell inspiron 1545. Its about 5 yrs old. Before I get into the problems, a few tthings to know about the laptop, it's battery barely works, it lasts for all of about 15 minutes so it is plugged in all the time and it gets very very hot. I've just formatted with windows 7. So the problem started a few weeks ago.. basically yhe screen randomly started flickering one day.. and after a few days it would flicker and then just go black. Then I figured out if u press f1 (or the button with the icon of a little laptop and a screen) it would turn back on for a few seconds but still go off. Doing this again and again I went to power options and changed it to power saving mode. That worked for a day but only on the lowest brightness setting. The next day it work but on for the brigtest setting. Now its just back to going black and me pressing f1 to see something for just a second. Oh i can press f2 and f12 on startup and in safe mode the screen is fine. Im bloody confused. All my documents are backed up but I need my laptop. Any suggestions?