So, do you want to remove the Sidebar completely?

If so simply edit your file ( most likely index.main.php ) and remove or comment out <div id="sidebar"></div> and alter the css, for the main content, as follows

#main {
	float: left;
	width: 100%;
	margin: 0 0 10px 0; padding: 0;
} 

Where is the index.main.php located. I have a index.php only and this does not contan any sidebar text.

Your skin is based on PixelGreen
In the pixelGreen folder there is a file named index.main.php

in that file there is the following... simply comment it out or delete it.
That will get rid of your sidebar

<?php
		// ------------------------- SIDEBAR INCLUDED HERE --------------------------
		skin_include( '_sidebar.inc.php' );
		// Note: You can customize the default BODY footer by copying the
		// _body_footer.inc.php file into the current skin folder.
		// ----------------------------- END OF SIDEBAR -----------------------------
		?>

Great! It Works. Thanks.

Ok...
cheers