Macbook Help

Hello every one, i own a white macbook which i bought in march 2008.
I have a problem with it,when i turn it on the screen just turns white & nothing else happens. The startup sound/tune can be heard but after that screen turns white it doesnt display the apple logo or anything.
i took it over to a computer shop they told me it might be some issue with the screen. i bought a mini hdmi cable & tired hooking it up on my tv, it still doesn't work.
Any body faced this problem ? is it worth fixing ? what might be the cost to fix ?
Any information will be appreciated !!
Thanks !!

 

I tired to do a safe boot & disk utility mode but nothing happened. It just doesnt go past the white screen. Could it be the hard drive has crashed ?