Delta Emulator only supports some systems and each one of those systems requires the ROMs file extension (.gba) to be a specific extension in order for Delta to recognize the system to which the ROM belongs. To make things easier for you, the extension is not case-sensitive.
When importing ROMs into Delta it is suggested that you import it as a zip (.zip) file. When creating the zip file, be sure to include only the ROM, if you zip a folder with a ROM inside the folder, it will fail to import.
|Game System||Supported Extensions|
|Game Boy Color||
|Game Boy Advance||
|Nintendo / Famicom||
|Super Nintendo / Super Famicom||