ok just a breif
after you got screw attack and go to gfs valhalla there is already a power core in your inv
you pickup one across the feild and now u have 2
you use one on the first door and swing across to the other side
then u go n some doors and whatnot and u find 2 power cores undone u only have 1
so u go back go upstairs and find a hallway with 2 doors on either side
one leads to yet another misle expansion and also releaseing a bunch of matured phazon larva
so u get the missle expansion and go down the other side here u find a door that needs a power core
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heres where i fucked up i used the only powercore i had on the place where u needed 2
and now i cant get it out.. and i really dont wanna shut off wii and redo that whole screw attack thing again.. yeah i didnt save..