1. XdeltaUI and Xdelta proper must be in the same folder.
2. There cannot be any accented or non-alphanumeric characters in the patch, source, or target file names or any folders they are contained within, except for the periods immediately prior to the file extension.
Heh, I get "xdelta3: target window checksum mismatch: XD3_INVALID_INPUT". Maybe you show, how get a nds hack in picture form.