HT5019 If my second display is not showing up on the graphics display window, yet the second display is showing a mirror image, how can I get it to recognize the second display and allow me to setup extended desktop?

10-11  Source: Network gathering  Views:3 

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I'm running 10.9.2 on a Power Mac from 2013.  I am using two identical HP monitors.  I have a Y adapter to connect the monitors.  Which I'm guessing means the computer is only seeing one display since there is only one display output. 
There are no PowerMacs from 2013.   The desktop tower from 2006 on got named Mac Pro.    The problem is probably the Y adapter.    You need a videocard with two display ports, or two videocards to be able to make an extended desktop from one to the other.  If you gave us the Y adapter make and model, we could tell if it supports screen spanning or not.
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