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should make the hard drive you are using as main boot device master.
Put the drive that does boot back in machine and boot it up look for file boot.ini
copy this file ,you may have to uncheck read only in file properties.
do search on internet for boot ini sequance
also will your at it under computer management make his drive/boot partition active.
on the cabling most first boot devices go at the very end of cable,not necessary ,but it helps
in bios first boot should be HDD 0