My Drupal installation was fine until I uploaded it into my web hosting. It always returned error 404 page (not found) every time I clicked on any admin section (i.e http://domain.com/admin/build, http://domain.com/admin/settings, etc).
I have tried bypassing clean URLs by using http://domain.com/?q=admin, renamed .htaccess file and so on. But all of my efforts still bring me the same error page.
After many minutes, I figured out that the problem was caused by the update module that always loaded every time I open admin section. Thus I decided to disable this module.
Just open PHPMyAdmin, click my database and run this query:
update system set status=0 where name='update'
And…… it works! All my admin sections are now working fine with this little trick.