Yeah, I get that too on my P4C800 Deluxe. As best as I can tell it's a bug in the BIOS, as it's plagued me since I bought the thing. Not to mention that making changes in the BIOS sometimes causes it to revert back to the factory settings. I've noticed that making any changes to the HDD settings will cause the checksum error, as well as wipe out any other custom configurations I've made to the BIOS. Decent board, but I'm less than thrilled about the software support for it. Asus seems to have slipped on this one issue, and I'm not too happy with the Promise drivers and their inability to install correctly (read: BSOD, file copy errors, etc) during an unattended setup. Heh, I'm not trying to whine