Turns on and off when booting

I scored a Laptop for nothing but it has a problem where it will not boot at all.

I am told at some stage someone replaced the RAM but and instantly stopped working.

When you try to turn it on it has power and attempts to boot but the screen stays black and after about 10 seconds it turns off again?

I have reinstalled original 4GB of RAM and removed the HDD to see if it would take me to the BIOS, but nothing seems to work.

Any suggestions would be helpful thanks.