Black screen off death ok in safe mode

Hi
This is my first post so here goes, we have been having problems with my wife's Toshiba satellite l300d (approx 5-6 yrs old) runing on vista svc pk 1 it boots up ok then you get the black screen but lap top is still runing i.e. hdd light is on and you can hear it, back light is still lite but no cursor or anything else showing the only way to do anything with it is to close it down with the on button held down, the weird thing is that it's ok all day if you boot it in safe mode, i have updated the graphics card driver still the same, tried removing battery holding down on button etc several times, tried disabling graphics card, and system restore, and power managment settings, there is no saying how long it is before it switches off the screen yesterday i thought i had cracked it it was fine for a couple of hours but then i turned off the charger by mistake (battery stuffed) went to reboot it and went black as soon as it had loaded.
any help on this one would be much appreciated
Cheers Jon