Hi, Alexander,
The DLP 12.0 can only support x64 operating system.
And, the Windows Server 2003 x64 is not on the support list.
You can check the System Requirement Guide of the DLP 12.0, and find out the description as below:
Symantec Data Loss Prevention supports the following operating systems for
Enforce Server and detection server computers:
■ Microsoft Windows Server 2008 R2, Enterprise Edition (64-bit)
■ Microsoft Windows Server 2008 R2, Standard Edition (64-bit)
■ Microsoft Windows Server 2008 R2 SP1, Enterprise Edition (64-bit)
■ Microsoft Windows Server 2008 R2 SP1, Standard Edition (64-bit)
■ Red Hat Enterprise Linux 5.6 through 5.9 (64-bit)