I have a Latitude E6510 and was having issues with it booting up intermittently.
Now the Dell logo appears with a progress bar below 50% complete. The BIOS revision is A06.
At this point it will go no further. Pressing F2 you get a Preparing to enter setup, but no setup.
Pressing F12 you get the Preparing one-time boot menu, but nothing else.
I have tried removing power and battery and holding down the power button for a few minutes and also doing the same after removing the bios battery as well. Same results.
Is there another way to get it to boot past the bios load?
Unplug the system, remove the battery and hold the power button for 30 sec. Remove and reinstall the memory modules and the hard drive.
Check all the USB ports for bent pins - a short in a pin inside the USB port will kill the POST sequence.
Try powering up on AC only - no battery. If it will, the battery is faulty.
If no power up, try one memory module at a time until you find the faulty module or socket and replace the module or the mainboard once you identify the faulty part.
if the memory tests OK, remove the hard drive and try powering up -- if the system will, replace the drive with a new one.
Failing all that, replace the mainboard.