The question I asked wasn't really correct. By saying 'Could this mean that I need a new graphics card?’ I meant: I don’t have a graphics card yet , should I buy (a new) one.
Also, what exactly do you mean by saying ‘what kind of footage is on the timeline?’. Do you mean the footage on the print screen in my post? That was just a clip of Air pollution. Almost all the clips are .avi files, but sometimes I use .wmv files too. (However, this problem never occurred on my Sony Vegas Pro 9)
(I have one hard drive)