R4i immediate HELP!!!!!?

OK i bought an r4i about a week ago but i couldn't play it until i got a micro SD. so when it came i downloaded a firmware but when i put the firmware file into my SD card and put it into my r4i turned on my ds and selected the r4i on the ds menu it said in a black screen with white font ``couldn't find_DS_MENU.SYS and it is really bothering me please tell me a Solution.THANKS