ConfigMgr (SCCM) 2012 Minimum system Requirements:

Configuration Manager 2012 RC2 native 64-bit applications no more supported on 32 Bit (OS and Hardware should be 64 Bit).

Site server and Site roles :

Windows Server 2008 (64-Bit)
Windows Server 2008 R2 (64-Bit)
Database (Below are listed for SCCM 2012 RC2):

Supported versions of SQL Server 2008(64-Bit) for RC2:

SQL Server 2008 SP2 Standard and Enterprise with CU7
SQL Server 2008 R2 SP1 and CU4
SQL Server Express 2008 R2 and CU4
If you are running SQL 2008 SP2, install CU7 from http://support.microsoft.com/kb/2617148
If you are running SQL Server 2008 R2 SP1, use CU4 from http://support.microsoft.com/kb/2633146

Distribution Point :

Windows server 2003 (including 32-bit)
windows Vista SP2 and Later (including 32-Bit)

ConfigMgr client :

windows XP SP2 & SP3 (32-Bit and 64-Bit)
Windows server 2003 SP2 (32-Bit and 64-Bit)
vista SP2 (32-Bit and 64-Bit)
Windows 7 TRM And SP1 (32-Bit and 64-Bit)
Windows 2008 SP2 (32-Bit and 64-Bit)
Windows 2008 R2 RTM and SP1 (64-bit)

Admin Console:

Vista SP2 (32-Bit and 64-Bit)
Widows 7 TRN and SP1 (32-Bit and 64-Bit)
Windows 7 SP1 (32-Bit and 64-Bit)
windows 2008 SP2 (32-Bit and 64-Bit)
windows 2008 R2 RTM & SP1 (64-bit)

For more information about Supported Configurations for Configuration Manager,please refer

http://technet.microsoft.com/en-us/library/gg682077.aspx#BKMK_SupConfigSiteSystemReq

The above all details are captured from Wally Mead session.