Evo D510C BIOS error

This Compaq Evo is not one of the small form factor (SFF) computers, it's called a 'convertible tower'... I guess because it can be a tower, or it can be a horizontal desktop PC also... whatever. It had an NVidia FX5500 128mb PCI card installed, and the owner of said PC just installed an NVidia FX6200 256mb AGP card, and the BIOS now gives this error upon boot up: Option ROM error: an add-on device has caused an option ROM error. If you have installed any new hardware, remove it. If this error does not appear, the new hardware is at fault. Contact support for more information. OK.... this isn't verbatim word-for-word, but it's really, really close to that. It says "Press F1 to continue booting, F10 for setup." So I played around with various BIOS settings, IRQs, and the like, to no avail. Pressing F1 will boot to Windows XP without problems, and the video card seems to be working just fine, as are the sound, ethernet, and everything else. Should we even be worried about the error from the BIOS? The PC seems to run just fine....
Thanks.

Oh yeah.... I looked into flashing the BIOS, but the newest version is already installed.....