computer turns on, but no display appears

[simon.hoegh]

So i have a rather old computer, which seems to work, as everything is spinning, BUT nothing shows up on my screen. On my motherboard 3 red lights are on on the back side.

 

[Ralston18]

Update your post to include full hardware specs and OS.

Have you tried another known working video cable?

Have you tried another known working monitor?

Have you tried the existing monitor on another computer?

Do you have the motherboard's User Guide/Manual. Need to find the meaning of the 3 red lights.