The column on the right is set to be 165 pixels wide - you'll need to set the width to zero. Edit wp_style.css, find#leftside, #rightside {
margin:0;
padding:0 10px 10px;
width:165px;
}
and replace with#leftside {
margin:0;
padding:0 10px 10px;
width:165px;
}
#rightside {
margin:0;
padding:0 10px 10px;
/*width:165px;*/
}
Another option would be to get rid of the container - edit template.html, find<!-- Right Sidebar Template -->
<div id="rightside">
<ul>
<li><h2>Links</h2>
<ul>
<li><a href="http://www.bullseyephotos.com/blog/" title="Read my blog">Blog</a></li>
<li><a href="#" title="Contact the Author">Contact</a></li>
<li><a href="http://forum.coppermine-gallery.net/" title="Coppermine Support Forum">CPG Support Forum</a></li>
<li><a href="http://www.mozilla.com/firefox/" title="Get Firefox">Get Firefox</a></li>
<li><a href="http://chrispederick.com/work/webdeveloper/" title="Web Developer Extension">Web Developer Extension</a></li>
</ul>
</li>
<li><h2>Theme Colors</h2>
<ul>
<li>
<p>
<FORM name="guideform">
<SELECT name="grootte" onChange="SetCookie(nameOfCookie, this.value, exp); doRefresh();"> <OPTION SELECTED value="2">--Color--
<OPTION value="1">Red
<OPTION value="2">Red2
<OPTION value="3">Blue
<OPTION value="4">Blue2
<OPTION value="5">Black
<OPTION value="6">Black2
<OPTION value="7">Green
<OPTION value="8">Green2
<OPTION value="9">Purple
<OPTION value="10">Purple2
<OPTION value="11">Orange
<OPTION value="12">Orange2
<OPTION value="13">Pink
</SELECT>
</FORM>
</p>
</li>
</ul>
</li>
</ul>
</div><!--End rightside-->
and replace with<!-- Right Sidebar Template -->
<!-- commented out to give the other columns more room
<div id="rightside">
<ul>
<li><h2>Links</h2>
<ul>
<li><a href="http://www.bullseyephotos.com/blog/" title="Read my blog">Blog</a></li>
<li><a href="#" title="Contact the Author">Contact</a></li>
<li><a href="http://forum.coppermine-gallery.net/" title="Coppermine Support Forum">CPG Support Forum</a></li>
<li><a href="http://www.mozilla.com/firefox/" title="Get Firefox">Get Firefox</a></li>
<li><a href="http://chrispederick.com/work/webdeveloper/" title="Web Developer Extension">Web Developer Extension</a></li>
</ul>
</li>
<li><h2>Theme Colors</h2>
<ul>
<li>
<p>
<FORM name="guideform">
<SELECT name="grootte" onChange="SetCookie(nameOfCookie, this.value, exp); doRefresh();"> <OPTION SELECTED value="2">--Color--
<OPTION value="1">Red
<OPTION value="2">Red2
<OPTION value="3">Blue
<OPTION value="4">Blue2
<OPTION value="5">Black
<OPTION value="6">Black2
<OPTION value="7">Green
<OPTION value="8">Green2
<OPTION value="9">Purple
<OPTION value="10">Purple2
<OPTION value="11">Orange
<OPTION value="12">Orange2
<OPTION value="13">Pink
</SELECT>
</FORM>
</p>
</li>
</ul>
</li>
</ul>
</div>
commented out to give the other columns more room -->
<!--End rightside-->
As suggested in the default text for the right column (the one you want to get rid of), you should really try the Web Developer Extension - it's the perfect tool to find out about such issues.
As your question is not related to the theme directly, you should have started a new thread on the regular themes support board. If my answer doesn't fully cover your issues, please do as suggested and start a new thread.