If keyboard lights won't respond and no beeps then it is the CPU/MB.
First off think overheat. Make sure the air passages are dusted and the laptop is sitting on a table or other surface that will allow cooling. A beadspread or your lap raise temperatures. (Yes, yes I know laptop implies it will work on your lap, but is actual a hazard there (google articles on burned weiners and lawsuits).)
Next you start fearing a major component like the MB. Ram is possible but normally a fatal crash from ram causes a reboot, not a white screen. But ot be sure run a ram burn in program for a couple hours (memtest).
The white screen really looks like avideo issue. The next time it dies try hitting caps lock or numlock. Pressing ctl-alt del tells you nothing since if the video is gone you won't know if it brought up task manager or not.