If the area they are going to is wide enough they should be next to each other by default.
However you use <center> twice, but three issues with this: 1) You shouldn't use <center> anymore it's depreciated... you use <div align="center"> now and end with </div>. 2) Even if you were to use <center> you would only use it once... 3) You didn't close the <center> tags with </center>.
I would try this code first:
Code:
<div align="center">
<A HREF="..//DBoftheMonth/Billygoat-Pro.jpg" target="_blank" title="Diamond Back of the Month for November 2010 - Pro (Survivor)"><IMG HEIGHT=150WIDTH=200 SRC="..//DBoftheMonth/Billygoat-Pro.jpg"></A><A HREF="..//DBoftheMonth/Billygoat-Pro.jpg" target="_blank" title="Diamond Back of the Month for November 2010 - Pro (Survivor)"><IMG HEIGHT=150WIDTH=200 SRC="..//DBoftheMonth/Billygoat-Pro.jpg"></A>
</div>
And see if that works.