Need to set computer display at 1024 x 768 but computer says out of range

That means that it is not capable of going that high.
Causes and solutions:
1) Video drivers have not been installed and you video is running in vga mode. Install the drivers.
2) You have onboard video and the memory is set too low. You need to go into the bios (try DEL at startup) and increase the amount of shared memory allocated to the video.
3) Video is just not capable of it (unlikely unless this is a very old machine or video card), buy the cheapest new video card you can find that fits. Anything new is capable of much higher resolutions than this.

I would have been more specific but not without knowing the make and model of your computer.

You might need to install or reinstall your video card driver