there is a emulator for nes but i dont know if it works on diamond. its called pocketNES, google it. i had it on my kaiser with a lot of roms like mk2,streetfighter etc. but i dont use it anymore and havnt tryd it on my diamond. but everthing you need is on the net.
But wait , i found it on my pc. heres the cab.
I also have the cab of the superNES emulator. here you go
I posted 2 zips with supermario3 and tekken2 in it for people to test, just unzip and put the .nes file on your internal storage,program will find it.