|Based on the information supplied, I'd suggest a process of elimination.|
Check that none of the pins are bent on the VGA cable (where it connects to the computer).
Try the monitor on a known working computer. At least this may rule out the monitor as the problem.
Does the machine have on-board video or a video card? If it's on-board, you may be able to use a video card. Be sure to disable the on-board video (in the BIOS). The choices of video card depend on the available types of slots on your motherboard.
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