Advent System restore problem

Hello,
Wonder if you could help, my daughter has this Advent PC which is given her grief.
It has been working well since she bought it 3 years ago.
When she turns it on, it goes to the Advent screen and there it stays.
I have tried to do a system restore using the Window XP back up disk, and this seems to go well and all the files appear to be loaded. Then it asks to restart the computer and when you press the yes button the screen goes blank and a NO SIGNAL sign comes up then its back to the Advent screen.
What do you think, could you me on this.

Thanks
Martin