Okay, but if you changed the extension from rar to bin your going to have to change it to rar. But if not follow the steps
For Linux nullDC 1.0.3
Step 1
> Extract the Folders from "dc_bios.bin"
> 3 Folders: NTSC-J, NTSC-U, PAL
> Copy "dc_boot.bin" & "dc_flash.bin" from NTSC-U into the Data Folder
> Start emulator up
For NullDC - Naomi edition 1.0.3 [To change the file extension]
Step 1
Go to where the Bios is > Look for "Tools" at the Top Left of the Window > Click "Folder Options" > Go to "View" > Look for "Hide extensions for known file types" > Check off the box so there is no check > Click "Ok"
Step 2
The "dc_boot.bin" should say "dc_boot.bin.rar" > Rename the whole thing "naomi_boot.bin" > Start the emulator and see if its working