problem with dell vostro 1310 and nvidia 8400M

Hi everyone, i hope someone can help me with this problem.

I have a Dell vostro 1310 Laptop with 32 bit vista and a 8400M nVidia chip.

Recently i have noticed performance issues when my girlfriend was playing Sims 3, and then one day i turned it on and all i got was a thick white line at the bottom of the screen.

i heard the OS start up so automatically i thought it was a damaged screen, but i had doubts so i plugged it into an external display via the vga port. it worked but everything appart worm the OS choice menu looks distorted beyond belief.

even the bios screen had multicoloured lines running down the screen.

The resolution is non existant, the screen only shows a 256 colour pallette and is heavily distorted. i barely managed to get to the device manager where i found the gfx card with an exclamation mark.

does anybody have suggestions? should i buy a new mobo or are repairs possible?

thanks in advance