Dead Screen Acer Aspire 8930G-864G64Bn

Hello all have a problem with the laptop in title it was delivered on 29/04/09 and if i try to boot with the mains power lead in i get to the account logon screen in vista but as soon as i click an account the screen goes dead. I can boot into any account in safe mode so i am pretty sure the panel is fine. Also if i boot from the battery i can get into any account but if i plug the mains lead in afterwards within a few minutes the screen goes dead again.

This laptop is for my daughter for her college and university (when she gets there )and it is important to get this sorted as she is a typical teen girl and gets disillusioned quickly if things don't work right for her. Any help is greatly appreciated and although i am very experienced with pc's i have had very little to do with laptops so i could simply be missing a setting i need to alter. I have changed the monitor in the nvidia control panel from multi to one and also tried the fn + f5 and fn + - & + to zero effect.