My computers config.
I5 + gigabyte b75 d3v, 8gb corsair ram and an old msi HD 5830 twin frozr. for some time my lg display is not showing anything after the startup. All fans are running. GPU and cpu everything is working. What should I do?

But you can see BIOS info when booting? So monitor or GPU is not fried?

What OS are you running? Linux? Windows? Are you using a proper HDMI cable?

If it shows the BIOS POST (power-on self-test) screen but nothing after that, then the default vga gear in the video card is working ok, but likely the high-resolution stuff is not. Have you tried another video card?