URGENT!!! Checkbox to Drodown?

Folks,

I have a code, which makes dynamic checkbox of categories:

<?php 

  $categories = get_categories( 'orderby=name&hierarchical=0&hide_empty=0' );

  $n = 1;

	  foreach ( $categories as $cat ): ?>

  <input type="checkbox" name="postcats[]" value="<?php echo $cat->cat_ID; ?>" >

	<?php 

	echo $cat->cat_name; 

  $n = $n +1;

endforeach; ?>

<input type="hidden" name="abb_num_cats" value="<?php echo $n;?>">

I need your help to Convert this Checkbox form to A dynamic Drop Down.

I know its possible, but am just not ale to achieve this. ??

May someone please help??