The February CTP of SQL Server 2008 has been released on Microsoft Download Center. From what I understand this CTP of SQL Server 2008 is feature complete. Please also check out the following article Breaking API changes in the February ‘08 CTP.
The download link to the CTP can be found below.
Microsoft SQL Server 2008, the next release of Microsoft SQL Server, provides a comprehensive data platform that is more secure, reliable, manageable and scalable for your mission critical applications, while enabling developers to create new applications that can store and consume any type of data on any device, and enabling all your users to make informed decisions with relevant insights.
- Supported Operating Systems: Windows Server 2003 Service Pack 2; Windows Server 2008; Windows Vista; Windows XP Service Pack 2
- For all download types
- *32-bit systems: Computer with Intel or compatible Pentium III 600 MHz or faster processor (1 GHz or faster is recommended)
- *64-bit systems: 1 GHz or higher processor
- *Minimum of 512 MB of RAM (1 GB or more is recommended)
- 675 MB of available hard disk space” (Microsoft).