ROMs, EMULATORs, & PS3 controllers

ok so i bought this USB adapater for PS2 controllers like a year or two back
and ive been using it to play on my PC with my brother with different
emulators and roms mostly the N64 one the emulator i use is Project64 and it
works fine but then i saw how the PS3 controller charger has a USB connection
so i thought i could use it the same as the PS2 USB adapater so i gave it a
shot and at first the PC installed the driver and i went to the controller
configuration and for controller 3 i put the PLAYSTATION3(R)CONTROLLER tht
the computer had installed but the controls were blank and i tried assigning
the controls but it wouldnt let me the controller wouldnt respond i pressed
the PS button but the lights on top wouldnt stop blinking like it wouldnt
assign a control slot so i was wondering can u even use the PS3 contoller
with emulators or am i doing it wrong? plz and thx in advance =]