Since you can get into bios, go over into the boot menu. Make sure you don't have as the "Other Boot Device" as INT18 Device.. but switch it to the SCSI/Onboard ATA. Make sure its also near the bottom of the boot list and the floppy is at the top.
Next is SCSI/ATA boot sequence, set it up to ATA first. Since you're trying to install a bios, I'd disable the "Load Onboard ATA Bios" (This is the auto detection for the promise controller)
And as an extra precaution, Say yes to reset the configuration data, this will tell the mobo bios to rescan the pnp devices.
If that fails, I'd check the jumpers on the mobo to see if Promise Raid is enabled. Set it back to normal (JP 13, 14 set to 1-2 for both)