First the difference in batteries between laptops and desktops in reference there is the board in a laptop should also see a small Lithium battery. The larger Lithium you recharge is the main power source while the cmos information stored on the bios eprom is maintained by the small battery there. The most commonly used battery is the CR2032 3v battery that replaces the 2032C and the LF1/2V as well. You should take it with you to any place where watch and pocket calculators are sold for matching it up.
With the Seagate at the end of the primary ide cable set as master you may have to set the WD drive to cable select on the middle connector. Try that either as slave or CS there to see which will work. If you are only trying to boot from the Seagate the need for two listing of hard drive in the bios boot order isn't necessary. The bios will automatically go to the first drive type set. On some boards you can bring the list of hard drives installed and simply one to the top of the list to be set as default once you save and exit the bios.
With the Seagate at the end of the primary ide cable set as master you may have to set the WD drive to cable select on the middle connector. Try that either as slave or CS there to see which will work. If you are only trying to boot from the Seagate the need for two listing of hard drive in the bios boot order isn't necessary. The bios will automatically go to the first drive type set. On some boards you can bring the list of hard drives installed and simply one to the top of the list to be set as default once you save and exit the bios.