if your using a 007 or MA with evox exploit you dont need to put the bios on C, you can pout it in the gamesave directory, just make a "bios" folder in the same directory as the evox default.xbe and the line will be
Item "Flash Evox BIOS",ID_Flash_Bios
if you using a dashboard exploit put the bios folder in C:\bios and use the same line (above) in evox