Step1: Download Nice Menus module from http://drupal.org/project/nice_menus
Step2: Extract the downloaded tar file to Drupal’s sites/all/modules directory.
Step3: Enable Nice Menus module from Drupal’s modules listing page at admin/build/modules (Menu: Administer > Site building > Modules).
Step4: Create sub-menus for the primary menu through the menu administration interface.
Step5: Configure the Nice Menu block from admin/build/block (Administer >Site building >Blocks). “Nice menu 1 (Nice menu)” and “Nice menu 2 (Nice menu)” are in the disabled section.
Step6: Click the 'configure' link against each to edit the block’s settings.
‘Menu Parent’ -> primary links ‘Menu Style -> right or left or down
Step8: Save block configuration
Step9: Clear cache.
The menu should now appear where you wanted it to.
To further customize this, edit the included CSS file.