What are systems requirements for drupal installation ?

System: 

- 3MB of disk space
- If you install many contributed modules and contributed themes, the actual disk space for your installation could easily be 40 MB or more (exclusive of database content, media, backups and other files).
Web Server
Drupal has been deployed successfully on both Apache and IIS.
Drupal is being developed to be web server independent, but we have limited or no reports of successful use on web servers not listed here.

Database server:
Recommended: MySQL 4.1 or MySQL 5.0
PostgreSQL 7.4 or higher

PHP:
Recommended: PHP 5.2.x
Required: PHP version 4.3.5 or higher (Contributed modules may not support this version of PHP)