For more information, please visit MicroSoft site link:
http://www.microsoft.com/windowsserver2003/evaluation/default.mspx

Run on most network in the world today and all most of the small to mid-sized business offices, this product is a major improvement on Windows 2000 Server with central file sharing, shadow copying and central faxing possibilities being the highlights. Currently, it is a good time to upgrade to Windows 2003 Server as it is now stable and affordable. We prefer this to Small Business Server as it limits the role of your server on the network only performing certain tasks rather than aggregating mail and other server roles on a network. This is our evaluation based on implemenetation on over a 150 networks in Southern California. Users on these networks vary from 5-500.

Hardware Requirements per MicroSoft:
http://www.microsoft.com/windowsserver2003/

Computer and processor
PC with a 133-MHz processor required; 550-MHz or faster processor
recommended(Windows Server 2003 Standard Edition supports up to
four processors on one server)
Memory - 128 MB of RAM required; 256 MB or more recommended;
4 GB maximum
Hard disk - 1.25 to 2 GB of available hard-disk space
Drive - CD-ROM or DVD-ROM drive
Display - VGA or hardware that supports console redirection
required; Super VGA supporting 800 x 600 or higher-resolution
monitor recommended

**Information provided by MicroSoft Corporation**