Problems with Pixels on screen after updating to windows 7

I have a Dell studio 1737 and updated it to windows 7 about 6 months ago, and ever since had a problem with the the pixels, when the laptop is first started up there is no problem the problem usually occurs after it has been on a while, although it happens straight away if I open Microsoft Word for some reason. 
The problem is that random lines of pixels seem to go out of place, that is they will just be in a random place normally to the left or right of where they are meant to be. The problem never happened with vista and i was wondering if anyone else has had this problem and what the solution would be, obviously i have tried updating drivers which didnt work any suggestions?.

Here is a picture of the problem

At first I just let it alone because it was not that bad but it has slowly started to annoy me more and more.