This is a GBA_Exploader plugin for the SCDSTWO.
The archive contains an .nds file but it isn't actually GBA_Exploader. It's a link file created by using Stormwave's plugin linker. GBA_Exploader needs to be downloaded seperately and put on the SD card at the root, along with it's own .ini file.
I have tested it on my DSLite and it works. I used GBA_Exploader 0.58b too but I don't suppose that'll matter as long as the file name of GBA_Exploader remains 'GBA_Exploader.nds' and is in the root of the SD..