Half-Life Brightness

Please help, have problem with brightness in half-life OPENGL… am running an asus geforce 1 SDR and latest version of HL + CS… Everything is dull and dark although the brightness is set to max with slider in HL… it is still playable but way to dark… my monitor is also set to max colour and brightness to the point where my desktop is too bright… Seems to be a HL problem… help with commands, suggestions etc… ta…