Start up screen has jagged red/white lines, then gets stuck on blank grey screen. How do I fix?

Hi There,

Having a problem starting up my Macbook Pro.

When I start up I get columns of pixel thin red lines on the screen while the wheel spins, then it goes to a plain grey screen and gets stuck.

I tried to use both the inbult recovery disk and an external USB recovery disc. Same red lines occur on screen as I go through the startup disc option page. I then choose wither recovery disc, it looks like it will boot from there. Then it goes to the blue screen and stalls indefinately again.

Has been working intermitently.. got it started and ran disk utility, it repaired permissions, and I thought it was all fixed, but not it is doing this again..

Do I need to do a complete format? I have a backup of my HDD.. so not the end of the world if I have to... but just wondering if anyone else had encountered this problem and had a fix?

If format is the only option, whats the best way, reload mountain lion from USB from scratch, then how do I recover my user account and apps from my old HDD backup without maybe getting the same problem again..

Thanks and please let me know if I can provide any more info to get some help with this..

Cheers

Chris