Basic Idea behind importing user in drupal is:-
1)Create dummy user object...
2)Call drupal's user_save function...
Actually, You need to create the user account array first...and then pass it to function user_save().
Module Of Interest:-
http://drupal.org/project/user_import
<?php
//$account = user_save('',$user_array);
$password = user_password($your_password);
$user = array(
'name' => $username,// Whatever you have
'pass' => $password,//Encr
'mail' => $email,//Your email here in variable
//'roles' => array( 3 => 3 ),//Add some role ID if you have and uncomment it if any
'status' => 1,// By default make users active
);
$account = user_save('', $account);// Call user_save function
watchdog(
'user',
'New user: %name (%email).',
array('%name' => $username, '%email' => $email),
WATCHDOG_NOTICE,
l(t('edit'), 'user/'. $account->uid .'/edit')
);//Add in Log
//Now $account is anobject with newly user information in it
?>