If you have a Chinese R4DS and want to put the English firmware on it, then you'll need to patch the _DS_MENU.DAT file before it'll work. Follow the instructions below to patch your _DS_MENU.DAT file.

1. Download the latest English firmware from www.r4ds.com
2. Download the latest language patcher
3. Extract firmware files and put the _DS_MENU.DAT file in the same directory as patch.exe and info.db
4. Run patch.exe
5. Type in name of dat file, _DS_MENU.DAT
6. It’ll ask you if you want to run it on M3 hardware, type N
7. It’ll ask you if you want to run it on Chinese or Japanese hardware, type 1
8. Copy the patched _DS_MENU.DAT to the root of your microSD with the other firmware files.
9. Done. Enjoy your new English R4 Revolution DS for the Nintendo DS Lite.

The instructions above were found here: http://ehsia.com/nintendo-ds/howto/r4-chinese-english