Depends on the scale and the capacity requirement, the recommended system requirement is as follows:
CPU : Pentium 2GHz Core Duo
RAM :1GB DDR2
Harddisk : 80GB
Microsoft
Windows® XP Professional or
Microsoft Windows® Server 2003 or
Microsoft Windows® Vista
Microsoft .Net framework 2.0
Microsoft SQL Server 2005 (optional)
Internet Information Service (IIS) (for reporting)