HP dv2500 doesn't boot but hard disk apparently workswon

[ladureld]

Hello, I have strange symptoms on my DV2500: It won't boot and show black screen and flashing cursor on top left corner. Now, if I place the hard disk inside an external USB enclosure and try to boot from it, I see that the hard disk is working but nothing shows up on the screen.... Any idea ? Many thanks for help

 

[AntiZig]

you can see that the harddisk is working via what? so far you haven't proven anything.
connect your HDD to another computer to verify that it's still working properly.

if HDD is fine you are likely having some type of motherboard problem