Hello,
You are trying to install a 32-bit version of Symantec Endpoint Protection onto a 64-bit operating system. You need to install a 64-bit version of SEP.
Please note that if you use Rafeeq's tip of installing a 64-bit version of SEP from the installation CD (SEPWin64) that the client will be unmanaged.
If you need the client to be managed, you should export a new 64-bit installation package from the Symantec Endpoint Protection Manager.
James