One or more of the cells in the battery is faulty - if you want to stop the flashing, that is the solution - you need a new battery.

Hi petarmarinov37,

Welcome to Dell community forum.

First thing you need to do is to disconnect the battery and ac adapter, then Press and hold the power button down for 10-15 seconds and then connect the battery back to the computer and try to turn on the computer .

Kindly do a BIOS update:

Link:

www.dell.com/.../latitude-d800

If this does not work try the following steps:

1)      Do you have light on AC adapter when it is connected to power socket only?

2)     If yes, then connect the adapter to laptop and check if light on adapter is still ON.

3)      If yes, try to do the following step, computer needs to turned off then try to press FN down and then while holding FN turn on the computer and keep holding the FN down if you see any message that says running diagnostics let go of the FN key and then complete the test, and reply back if there is any error message.

4)      Try using the adapter without the battery and check if the computer stays on.

If you have active warranty, you can contact me directly by clicking on my user name, add me as your friend, and send me the system service tag and phone # with address.