Vista Desktop Screen Issue

Hi there,
I have an issue where, ever since I installed Vista, my desktop image has a small black line running across the screen at various times and various places. It changes location depending on if I run a different application or if I reboot. It may not change at all sometimes. Other times, there are even 2 or 3 of these black lines and I cannot seem to find anything about this issue. I can't even take a screen shot. If I had to replicate the problem to give you a visual, all I can do is use a sample image of a Vista wallpaper (or any wallpaper, doesn't matter what you use) and draw a line about one inch long, horizontally, on any place of the image, relatively closer to the top and that's exactly what it looks like.

Any help would be greatly appreciated!

 

I'm having the same problem with my computer with Vista Home Premium. I have a Dell WFP2007 monitor and a NVIDIA GeForce 7900GS graphics card. Any help on this issue would be greatly appreciated. Thank You!!!