How to display the node id as a field (with label)
Create a template for the content type and use &lt;?php print $node-&gt;nid; ?&gt;

Make a copy of node.tpl.php from modules/system and paste in your theme directory.  Copy the code from inside node.tpl.php and create a new file called "node--YOURTYPE.tpl.php" (replace YOURTYPE with the name of the content type).

Inside that file you can place &lt;?php print $node-&gt;nid; ?&gt; wherever you want the nid to be seen.  You can add a label, wrap it in HTML to style it, whatever you like. Save the file and clear the cache to see the changes.  Take a look at a node of that content type and you will see the node's nid.