Dan, thanks for the reply. I think this board does support ECC functionality because I saw some info on Intel's site about Intel's P4 motherboards based on the same chipset as the Asus P4T533-C. Intel specifically mentions the ECC functionality on their motherboard, so I think it's probably supported on all boards that use that chipset.
I have seen motherboards that let you use ECC memory but didn't support ECC functionality.