Windows Small Business Server 2008 (Windows SBS 2008) is an integrated server solution that helps you protect your business data, increase productivity and present a more professional image to customers. By providing many of the features used by larger companies –e-mail, an Internet connectivity, internal Web sites, remote access, support for mobile devices, file and printer sharing, backup, and restore–Windows SBS 2008 gives you the tools you need to help grow your business.
Windows SBS 2008 is available in two editions: Standard and Premium.
Standard Edition includes the software to install the primary Small Business Server. To install Standard Edition, you will need to download:

• SBS2008_RC0_ENU_DVD1.iso - Small Business Server Installation

Premium Edition includes software to install an additional Windows Server (either x86 or x64) for your domain, with the option of running SQL Server. To install Premium Edition, you will need to download:

• SBS2008_RC0_ENU_DVD1.iso - Small Business Server Installation
• SBS2008_RC0_ENU_DVD2.iso - Additional Server Installation x86
• SBS2008_RC0_ENU_DVD3.iso - Additional Server Installation x64
• SBS2008_RC0_ENU_DVD4.iso - SQL Server 2008 for Small Business CTP6

More information about Windows SBS 2008 editions is available here.

Download here