Vertical lines and image gradients appearing on G5? PLEASE HELP!

Hello! I have been experiencing some issues with my G5 recently, in which I haven't been able to find very much information at all on. So, I figured I'd try to get everything sorted out here, and see if any one knows how I can fix my problem?

Vertical lines ;

From what I've seen, this seems to be a pretty common problem. It started one day when I discovered just a single pixel blue line running down the very center of my screen. After a while I learned to ignore it, but overtime, more began to appear. I am now up to 33 of these lines spanning in various different spots on the screen, all different colors. Again, I've learned to cope, but with time, more seem to be appearing. I'm just wondering how I can fix it, before it gets too bad?

Image gradients ;

I have never been able to find anyone with a problem even slightly like this on my type of computer, so I'm curious to know if anyone else has ever had this problem, or have seen of anyone who has? It seems that not too long after the vertical lines began showing up, that a weird sort of gradient type texture has appeared on many of the default mac images, along with images and videos in both preview and iMovie/quicktime. Here is an example of part of my screen:

I find that the places it effects the most are in games, such as Minecraft or the Sims 2, in which I used to play a lot a few years back. It also effects exported photos and videos if uploaded to the internet. For example, I uploaded a video to YouTube recently, in which I played back on my phone a few hours later to find that it had the gradient on it as well, only a red version. My brother seems to think its a virus, but I'm not sure? Does anyone know how I can fix this?

Thank you for taking the time to read!