A problem with my M1330

I really need help guys

while am operating normally on my xps some blue lines start 2 be seen in the middile of the screen then goes orange then boom screen goes black

i tried closing the lid and opening it

i saw dumping physical memory and and Error message system halted

and then the laptop restarted and i lost all my data

after restart windows say error with the graphics card and says this "nvlddmkm"

my windows is vista home premium and its virus free and i reinstalled coz i thought the error was with it but still the same

i tried downloading latest drivers for my graphics card nvidia gforce 8400 Gs 128 from dell drivers but there is no use

also from nvidia there driver doenst want 2 be installed ! sayin u arent operating on vista 32 however i choosed vista 32 bit

still the same

note (it happens suddenly while operating normally on the computer without  fancy things or heavy games nothin )

help me guys its really annoying

thanks in advance

hope some1 helps