Yep, your backlight inverter or the tubes have gone, but more likely the Inverter......... this is an easy fix and not to expensive, you could try Ebay for one and do it yourself..
Although this is an American site they are very good for this type of thing, see link and select make then model, they have a guide on the top of the page too.....
http://www.lcdparts.net/LaptopInverter2.aspx
Again dependant on model they have idiot guides with pictures on how to do it...
http://www.lcdparts.net/howto/inverterinstallation.aspx