back light suddenly disappears

Hello guys,i have a problem with my macbook 2008 that i had been using for the last 5 years.I start it up and the back light comes for just 5 seconds and suddenly goes out.i have tried using the keys to brighten it up but nothing seems to be working.I can still see the the contents on the window but they are barely possible to read.Did any one have such a problem? I was due to present a project soon and your valuable help is needed!! Thank you! yayu