Maybe the installer assume that your current settings are the best one available, even if they are way lower than possible.
Set the colour depth to 32 bits if it's set to a lower value like 16 or 8 bits.
Try using the native resolution of the monitor. For an LCD one, it's the higher one available.
Maybe the video card can't handle the required resolution or the monitor don't.
Try with a borrowed monitor to see if things work better.
Check the capability of the video card.
If you need to replace the video card, unless you are in heavy playing, a mid range is more than enough, and some entry level ones may be good enough for your needs. You don't need to spend more than $70 to $80.