Drupal has certain environmental requirements that need to be met in order to operate properly. Before going through the time and effort to install it, check with the server administrator to ensure that the following points are all true:
Web server—Apache 1.3 or 2.x (it is possible to run Drupal on Microsoft IIS, but there are so many caveats that it isn't worth the effort)
PHP 5.2 or higher
mysql, mysqli or pgsql enabled in PHP
PHP settings
memory_limit: 64M
(some hosting accounts do not allow the memory to be overridden from the default 16M, so be careful)register globals: Off
session.save_handler: user
error_reporting: E_ALL
safe_mode: Off
session.auto_start: 0
.htaccess AllowOverride enabled