Create a folder usercount in the location:sites/all/modules/

Create a file usercount.info in the location:sites/all/modules/usercount and add tho following code

	name = User Count
	description = Field API to add fields to entities like nodes and users.
	package = Custom Block
	version = VERSION
	core = 7.x
	configure = admin/structure/usercount

	; Information added by drupal.org packaging script on 2012-02-01
	version = "7.12"
	project = "drupal"
	datestamp = "1328134560"
 

Create a folder usercount.module in the location:sites/all/modules/usercount/

 <?php

/**
 * @file
 * Enables the use of personal and site-wide contact forms.
 */
/**
 * Implements hook_help().
 */
global $uerr;
$_FILES;

function usercount_help($path, $arg) {
    switch ($path) {
        case 'admin/help#usercount':
            $output = '';
            $output .= '<dl>';
            $output .= '<dt>' . t('View total user') . '</dt>';
            $output .= '</dl>';
            return $output;
        case 'admin/structure/usercount':
            $output = '<p>' . t('View total user') . '</p>';
            return $output;
    }
}


function usercount_block_info() {
    $blocks['usercount'] = array(
        'info' => t('View Total User')
    );
    return $blocks;
}


function usercount_block_view($delta='') {

    $block = array();
    switch ($delta) {
        case "usercount":
            $block['subject'] = t("View Total Product ");
            $block['content'] = drupal_render(drupal_get_form('usercount_block_contents'));
            break;
    }
    return $block;
}

function usercount_block_contents($form, &$state) {
    
    $result = db_select('users')
	         ->fields('users')
			 ->execute();
   $count = count($result->fetchAll());
    $form = array();
	
	$path = drupal_get_path('module', 'usercount');
       // Attach the CSS and JS to the form
    $form['#attached'] = array(
    'css' => array(
    'type' => 'file',
    'data' => $path .'/demos.css'
    ),
    'js' => array(
    'type' => 'file',
    'data1' => $path .'/jquery-1.7.2.js',
    'data2' => $path .'/jquery.ui.core.js',
    'data3' => $path .'/jquery.ui.accordion.js',
    'data4' => $path .'/jquery.ui.mouse.js',
    'data5' => $path .'/jquery.ui.resizable.js',
    'data6' => $path .'/jquery.ui.widget.js'
    ),
    );
	
	
    $form['table'] = array(
        '#prefix' => '<div id="footer"><p>Total users: '.$count
    );
	
	$form['tableend'] = array(
        '#suffix' => '</p></div>'
    );
	
	return $form;

}
?>
 

Add this files demos.css,jquery-1.7.2.js,jquery.ui.widget.js,jquery.ui.resizable.js,jquery.ui.core.js in the location:sites/all/modules/usercount/