I've recently started playing around with XNA on my brand new laptop (my new development machine) and I'm liking what it can do. However while going through the samples from creators.xna.com I loaded up the PerPixelLighting sample, built it and ran it. Everything was going fine, it renders a sphere in the middle of a large grid and shows off different techniques. However, after about 30 seconds of toying around, I noticed the grid start to flash slightly and eventually the display completely locked up for a few seconds, then blank out, then come back to normal with vista reporting an error saying that the display drivers stopped responding but it recovered okay. I found that not rendering the grid means that the sample runs fine so I'm wondering if anyone has any insight on why this is happening? The grid is drawn using a series of draw primitives call to draw several linelists. As for the laptop, its a Dell inspiron 1520 with an NVidia GeForce 8600M GT vid card. Not sure what else could be relevant. If anyone has any ideas, or has experienced this before I'd love to hear about it.