Can not power up or shut down D600 Latitude

Try flexing the whole bottom assembly. that is with the laptop open put your knee in the middle and grab the unit with one hand on the corner closest to you and the other near the screen and put enough pressure to "flex " the mobo right after you push the start button if it doesn't start try it the other way... this has been working for my grandsons d600 for 6 months. i tried a new switch board because the guy that sold me the mobo said the plug for that is known to crack and that didn't fix it. good luck ps you will know it has worked when the 3 lock lights go out and the power light stays on.

try removing the battery (keep ac power), test
if nothing, try the opposite,
remove both ac power and battery test,
for some reason holding down f10 and cursing at the machine seems to help. Mine does this but typically will boot after a few attempts (and lots of cursing)

purple function key next to the ctrl key
press that down and hold
press the num lock (toggle)
press the scroll lk (toggle)
press white cap lock only
See if any of these change the lighted lock indicator.
I assume that was what you mentioned in a focus of the request

Please perform the steps mentioned in the link below:

Step by Step Troubleshooting

when your computer is freezes up then you download registry mechani it can improve your performance

If your batterry is 3 years old u have to replace it. Its not charging properly

This problem can be solved by scanning the computer from viruses.
thanks..

The Caps Lock LED flashing indicates a Motherboard failure on the system

You could shut down your by forced shut down. to do this, press and hold the power button for 5 seconds, during which a long beep is heard. The system will shut down.
Try reinstalling the operating system to resolve this problem

you can try to replace the motherboard, which is apparently totally UnHappy