When pressing the power button the laptop begins to boot (all the indicator lights cycle and I hear the optical drive start) but the laptop then shuts off after ~3-4 seconds.  I never even get to the Dell screen.  I have tried to run the LCD BIST by turning the computer on while pressing the key and I get the four color sequence.  I then tried to run the PSA diagnostics by holding and powering on the laptop.  However, it never goes through any diagnostics.  It just boots up as previously described.  I'm assuming I have a hardware problem but I'm not sure how to determine what's wrong.  Any help would be appreciated.  Thanks!