Those are Nintendo Official screw you need a Tri-Wing screwdriver for those.
http://www.play-asia.com/paOS-13-71-...fr-70-1fe.html
and if you need to Open a N64 or Snes you will need these:
http://www.play-asia.com/paOS-13-71-...fr-70-14z.html
http://www.play-asia.com/paOS-13-71-...fr-70-140.html
If you don't want to buy those you can try with a Small Pen-Size Flat screwdriver and stick it between 2 of the 3 Prongs to try and make it un-screw.