Darren,
Although Till's way will work, there's a much easier way with a simple nested table. Basically, you make the outer table a background color with a cellspacing of 1 (to create the outline) then make another table with set bgcolor props...see below.
Code:
<!-- start outside table for outline -->
<table bgcolor="#000000" cellspacing=0 cellpadding=1 border=0><tr><td>
<!-- start inner table for content -->
<table bgcolor="#EEEEEE" cellspacing=0 cellpadding=5 border=0>
<!-- upper cell: -->
<tr><td bgcolor="#888888">
<p align="center"><font face="Verdana, Arial, Helvetica, Sans" size=2 color="#EEEEEE">Moo</font></p>
</td></tr>
<!-- lower cell: -->
<tr><td>
<p><font face="Verdana, Arial, Helvetica, Sans" size=2>Blah blah blah, etc.</font></p>
</td></tr>
</table>
<!-- end inner table for content -->
</table>
<!-- end outside table for outline -->
I find that much easier than trying to play around with spacers in cells. This also allows you to have a cellpadding amount (margin) for the inner table (so your content isn't right up against the outside).
Hope that helps,
Nate
P.S. The corners on deskmod are graphics, and that gets a lot more complicated (personally, I hate to use graphics the way deskmod does just because of browser errors and misrenderings).