http://www.icyphoenix.com/viewtopic.php?f=36&t=2227&p=55381#p55381
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Joshua203
Sun 11 Mar, 2012 12:08

Re: Sitelogo
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[quote user="Mighty Gorgon" post="16279"]Edit all the overall_header*.tpl and move the logo code into the central TD of the header table.[/quote]

The above means that this part in the code would look something like this:
[code linenumbers=false]<table id="forumtable" cellspacing="0" cellpadding="0">
<!-- IF GT_BLOCK -->
<tr><td width="100%" colspan="3"><!-- BEGIN ghtop_blocks_row -->{ghtop_blocks_row.CMS_BLOCK}<!-- END ghtop_blocks_row --></td></tr>
<!-- ENDIF -->
<tr>
	<td width="100%" colspan="3" valign="top">
		<div id="top_logo">
		<table class="" width="100%" cellspacing="0" cellpadding="0" border="0">
		<tr>
		<td align="left" height="100%" valign="middle">
		<!-- IF GL_BLOCK -->
		<!-- BEGIN ghleft_blocks_row -->{ghleft_blocks_row.OUTPUT}<!-- END ghleft_blocks_row -->
		<!-- ELSE -->&nbsp;
		<!-- ENDIF -->
		</td>
		<td align="center" valign="middle">
		<div id="logo-img"><a href="{FULL_SITE_PATH}{U_PORTAL}" title="{L_HOME}"><img src="{FULL_SITE_PATH}{SITELOGO}" alt="{L_HOME}" title="{L_HOME}" /></a></div>    
		<!-- IF S_HEADER_BANNER --><center><br />{HEADER_BANNER_CODE}</center><!-- ELSE -->&nbsp;<!-- ENDIF --></td>
		<td align="right" valign="middle">
		<!-- <div class="sitedes"><h1>{SITENAME}</h1><h2>{SITE_DESCRIPTION}</h2></div> -->
		<!-- IF GR_BLOCK -->
		<!-- BEGIN ghright_blocks_row -->{ghright_blocks_row.OUTPUT}<!-- END ghright_blocks_row -->
		<!-- ELSE -->
		<!-- IF S_LOGGED_IN -->&nbsp;<!-- ELSE -->&nbsp;<!-- ENDIF -->
		<!-- ENDIF -->
		</td>
		</tr>
		</table>[/code]

And because the logo will then be above the menu block buttons, you should probably change style_p_black.css too (because your logo will start overlapping the links): 

[code linenumbers=false]#top_logo {
	border: 0px solid #181818;
	background: #000000 url('images/p_black/top_header.png') repeat-x;
	height: 150px;
}[/code]
Adjust the height until you have the desired effect ;)
(or cut the height of the image used or play with z-index until it looks good)