!!! IMPORANT...you HAVE to have a product listed for the Main Cat or Subcats to pick up!!!
Can you explain that in a different way, I don't understand.
Do you mean the product has to be enabled or it has to exist in another category?

Browsers: The code formatting and accompanying css in the original version available for download is somewhat "inelegant".
I have since cleaned it up a bit which (illogically) fixed an issue with the main search at the end of the bar requiring a significant negative top margin in IE6 and IE7 to line it up correctly
I did not have any problems with other browsers though.
Your page width may cause overflow issues.

Updated code:
PHP Code:
<!--BOF Product Finder-->
<div class="clearBoth"></div>
<div id="product_finder_wrapper">
  <div id="product_finder">
    <?php 
     
echo "<form action=''>";            
?>
    <ul>
      <?php
   
echo "<li>";
   
$model1[]=array('id'=>'','text'=>TEXT_PLEASE_SELECT);
     if(isset(
$_REQUEST['cPath1'])){
     
$value=$_REQUEST['cPath1'];
     }     
     echo 
'<span id="pf_title">'.strip_tags(TEXT_FIND_ALL_PRODUCTS).'</span>
     <span class="pf_selectbox_name">'
.TEXT_MAKE '</span>' zen_draw_pull_down_menu('cPath1',array_merge($model1,zen_get_category_tree()),$value'id="cPath" class="searchSelectClass"'); 
     echo 
"</li>";
   
    echo 
"<li>";   
    echo 
"<noscript>";
    echo 
zen_my_image_submit(PF_NOSCRIPT_SUBMIT);
//echo zen_draw_input_field("submitButton","Go",'','submit');
         
if($_REQUEST['cPath1']!=""){
               
$value=$_REQUEST['cPath1'];
               
$dropdownArray=zen_get_category_tree($value);
         }
echo 
"</noscript>";
echo 
"</li>";      

echo 
"<li>";
      
$modulePath="".DIR_WS_CATALOG;
      echo 
zen_draw_hidden_field('basemodulepath',$modulePath,'id="basemodulepath" ');
     
$model=array();
     
$model[]=array('id'=>'',
                     
'text'=>TEXT_PLEASE_SELECT
                     
);
       if(
$_REQUEST['cPath1']!=""){
        
$model=array_merge($model,$dropdownArray);
        }
    if(isset(
$_REQUEST['select_model'])){
    
$value=$_REQUEST['select_model'];
    }
     echo 
'<span class="pf_selectbox_name">' TEXT_MODEL .'</span>' 
     
zen_draw_pull_down_menu('select_model'$model$value,  'id="select_model" class="searchSelectClass"'); 
echo 
"</li>";

echo 
"<li>";
echo 
"<noscript>";
if(
$_REQUEST['select_model']!=""){
               
$value=$_REQUEST['select_model'];
               
$dropdownArray=zen_get_category_tree($value); 
         }
echo 
zen_my_image_submit(PF_NOSCRIPT_SUBMIT);         
//echo zen_draw_input_field("submitButton","Go",'','submit');
echo "</noscript>";
echo 
"</li>";

echo 
"<li>";
     
$year=array();
     
$year[]=array('id'=>'',
                     
'text'=>TEXT_PLEASE_SELECT
                     
);
      if(
$_REQUEST['select_model']!=""){
        
$year=array_merge($year,$dropdownArray);
        }                                  
if(isset(
$_REQUEST['cPath'])){
          
$value=$_REQUEST['cPath'];
}
if(
$_REQUEST['select_model']!=""){
     echo 
'<span class="pf_selectbox_name">' TEXT_YEAR '</span>' 
     
zen_draw_pull_down_menu('cPath',$year $value,  'id="select_year" class="searchSelectClass"');
     }
else {
     echo 
'<span class="pf_selectbox_name">' TEXT_YEAR .'</span>' .
     
zen_draw_pull_down_menu('cPath22',$year $value,  'id="select_year" class="searchSelectClass"');
}     
echo 
"</li>";

echo 
"<li>";
echo 
"<noscript>";
if(
$_REQUEST['cPath']!=""){
         
$value=$_REQUEST['cPath'];
         }
echo 
zen_my_image_submit(PF_NOSCRIPT_SUBMIT);
echo 
"</noscript>";
echo 
"</li>";
?>
</ul>
    </form>
    <div id="navMainSearch">
      <?php require(DIR_WS_MODULES 'sideboxes/search_header.php'); ?>
    </div>
    <!--close navMainSearch div--> 
  </div>
  <!--close product_finder div--> 
</div>
<!--close product_finder_wrapper div-->
<div class="clearBoth"></div>
<!--EOF Product Finder-->
Updated style_product_finder.css
Note this is MY unadulterated css with white text, I include it so you can edit the correct selectors.

@charset "utf-8";
/* CSS Document */
/*styles for Product Finder mod*/
#product_finder_wrapper {
background-image:url(../images/background_bg.gif);
background-repeat:repeat;
margin:0 auto;
width:960px;
padding:10px 0 0 0;
border-top-width: 1px;
border-top-style: solid;
border-top-color: white;
}
#product_finder {
background-image: url(../images/search_bar.png);
background-repeat:no-repeat;
height:41px;
width:100%;
padding:8px 0 0 0;/*otherwise text is top-aligned*/
font-weight:bold;
color:#FFFFFF;
}
#product_finder ul {
}
#product_finder ul li {
list-style:none;
float:left;
margin-right:10px;/*space between the drop-down items*/
}
#pf_title {/*"Show Products for..."*/
font-weight:bold;
font-family:arial;
font-size:14px;
color:#FFFFFF;
margin-right:5px;
}
.pf_selectbox_name {/*text in front of drop-down select box*/
font-weight:bold;
font-family:arial;
font-size:13px;
color:#FFFFFF;
margin-right:2px;/*space beween the drop-down name and the drop-down box*/
}
#navMainSearch {
float: right;
}
regards
Steve