Computer starts /w black screen.

Hello everyone.
I am desesperatly in need of help.
I am having trouble with my computer, obviously;
My computer is starting up, fans, powersupply, even detect the dvd drive, but my screen is just black…with the flashing power buttom of the screen.

My computer processor is Athlon XP 1800
I have 512 mb ram,
It is about 5-6 years old, I have no idea what my motherboard is, since it’s my friend who gave it to me.
I have a geforce 2 as a graphic card,and some shitty soundcard.
2 harddrives.

So this is what I did so far :
I checked to see if all the cables were plugged ok(yes many times..)
Resetted my CMOS memory
Checked for bent pins all over my mother board and PCI and AGP slots.

Any ideas?