All - We have successfully installed Siebel CRM on Windows 2008 32 bit. Though our intent was to install Windows 2008 64 bit we faced multiple issues with SISNAPI. So we decided to install Hyper-V running Windows 2008 32 bit on a Windows 2008 R2 - 64 bit.
Siebel functionalities are working as expected. We specialize in Siebel virtualizations, if you have any questions please feel free to contact me at email@example.com