A work around to playing Powder on the Wiz is using the GBA emulator and playing the zipped version (It doesn't work unzipped for some reason) of the Powder rom. Still, no dice if you don't have the GBA bios.
Have you downloaded the version of the emulator specifically for the Wiz? The plain old GP2X versions don't work on the Wiz.
The only emulator that I know of that has been ported to the Wiz that needs a bios is gpSP. The bios is a file in the Gameboy Advanced. It is needed to make the emulator...