this should be pretty simple. find the bit of code in the header.php around line 21 that starts with:
<div id="searchdiv"><?php include (TEMPLATEPATH . '/searchform.php'); ?></div>
and make it
<!--div id="searchdiv"--><!--?php include (TEMPLATEPATH . '/searchform.php'); ?--><!--/div-->
(I am leaving the line effectively the same, merely commenting out the code that you are not interested in. This way, all you have to do is remove the !-- and -- later, and you are back to the way you were.)
Paul
