laptop not starting

I have an older Dell Latitude P2 laptop that is not booting or even starting.
When I push the start button the light comes on for about 3 sec. but that is all. I don't hear anything coming from the laptop.
I have tried removing the battery, I have removed the optical drive. I have removed and reseated the Ram.
If the hard drive fails doesn't it still go into the first stages of booting still?
What things can I check?

 

A lappy or desktop will power on & post an error if the hard drive fails.

Since when has it stopped starting at all? If it's been a long while, it might need to be serviced by a qualified technician.

 

There is power going to laptop. The light comes on for a few sec. then dies.

 

If this problem occurs while the computer is connected to the AC power supply I would suggest that the microprocessor has failed.

If this occurs without the AC power supply connected it may be possible the battery is failing, even though the power light comes on for a few seconds.

 

Hi. Might try removing the battery, (gently) cleaning the terminals, then replace the battery. I have seen a poor battery connection cause that kind of stuff. Good night and good luck.