I can't help but think that we've got to be missing something simple here.
I think we need to compare exactly what you bios shows about your drive configuration and what shows on the "Settings" tab on each drive in Device Manager.
You proably already know this but:
As soon as the bios displays the drives detected press (very quickly) the [Pause/Break] button and write down the displayed info(Drive Name, Primary/Secondary, Master/Slave). All your drives should be shown(*), if not as soon as you "Press Any Key" to continue running the bios press the[Delete] key to enter the Bios Setup Program, the drive info. is usually a page/screen named "Standard CMOS Settings". If you can't get into the bios setup on this pass let it finish rebooting and then restart the PC again and go directly to the Bios Setup Program and write down the info needed and then exit setup.
(*) Some bios will not show manually configured drives on the startup screen.
I can see from earlier posts that you know enough about Device Manager so, onward.
I know that you've proably done all of this about a hundred times by now but, please humor us we may solve this yet. Please post your findings.
:ufo: :ufo: :ufo: