Well first i tried this too but its now clear!
The r4 or anyother slot-1 flashcard can NOT play gba roms if you want to play you have to buy a slot-2 flashcard.
You had to informate because there are many topics that all say "No you can't play gba roms on r4!"
I hope i made myself clear if not read the rules about duble posts!
Greetz Wok247