Friendly reminder to update your BIOS and device drivers every once in a while. Sadly enough it is not sufficient to only ensure all operating system, anti-virus, and browser updates are up to date.
My Dell Latitude D630 recently started blue screening and crashing when playing videos. It got annoying pretty quickly, so I updated the BIOS and device drivers in the hopes that would resolve the issue. This week it got a lot worst, in fact it would not even boot properly at times, instead just displaying lines. A temporary fix was to remove the battery and power cord, hold the on button for 30 seconds, and replace the battery. Not exactly sure what that did, but worked for at least one more boot.
Unfortunately after some searching, it looks like the GPU has failed due to a common overheating issue with this model. The fix is to update the BIOS before it fails. After it fails it requires a hardware replacement. More information at http://en.community.dell.com/blogs/direct2dell/archive/2008/07/25 /nvidia-gpu-update-for-dell-laptop- owners.aspx