Curious. I'm not very familiar with Mandriva but I'll have a bash. Either Mandriva thinks you're using a generic monitor that can only display 1024x768 at the most, or it has the monitor right but incorrectly thinks its highest resolution is 1024.768.
Try Control Centre -> Hardware -> Graphics. If I recall correctly, there should be an option there to tell it which monitor you're using. Hopefully the current selection is some generic screen, and you're able to select either your monitor or something close to it that is capable of the resolution you want.
If this fails, we might have to delve into xorg.conf.
By the way, I'm not even remotely an expert in Linux; I'm just a desktop user who prefers Linux to any other OS. Maybe someone much more knowledgable than me will happen upon this thread with better advice.
Try Control Centre -> Hardware -> Graphics. If I recall correctly, there should be an option there to tell it which monitor you're using. Hopefully the current selection is some generic screen, and you're able to select either your monitor or something close to it that is capable of the resolution you want.
If this fails, we might have to delve into xorg.conf.
By the way, I'm not even remotely an expert in Linux; I'm just a desktop user who prefers Linux to any other OS. Maybe someone much more knowledgable than me will happen upon this thread with better advice.