I need help wiring a gfci outlet.?

Is it possible that you have a ground fault circuit breaker in your electrical box feeding this GFCI recepticle? Typical circuit breakers have no wires of their own. But a GFI breaker has its own white wire. If that white wire is not connected the breaker will work like any ordinary one (no GFI). It is important that you sort out the origin of each of the white wires in order to put it together correctly. Also you need to be able to turn off the heat from the black source wire. The other black has a white partner and they belong on the bottom of the GFCI receptacle. The supply black and its white partner belong on the top of the receptacle. The Receptacle is up-right when the round ground outlet hole is pointing down. The odd white wire should originate from the ground buss along with the one that is paired with the hot black. The other white wire goes to another outlet in the room. And it appears hot because something is plugged in over there and you have not yet found the proper circuit breaker to kill power to this one, you are working on. OR, or maybe the other outlet in the room is receiving the power first and then sending it on to this GFCI here. What I'd do, is get the power turned off first. Take all the wires off and out in the open. See what else is not working while it is off. All this stuff is daisy chained together, see? Try to look farther up on the wire bundles and tell which Black and whites are paired together.

The correct wiring of a GFCI outlet is from the breaker, Black on the TOP brass terminal, White on the TOP silver terminal, bare or green Ground on green terminal. The branch circuits (all the other outlets that are protected by this GFCI outlet) should be on the BOTTOM terminals. Sounds like someone attempted to use the neutral in the box there instead of where it originated. It will be hot if it is a non-switched load, or the switch for that load is on. Most likely a light that may have been added. You should only have 2 black, 2 white and 1 green or bare wire in that gang box. A GFCI will not work properly if any loads are taken off the top terminals, it will not be able to protect against a ground fault.You need to isolate all your wires, make sure you know which are your supply wires and which are your load wires, and that you can SAFELY isolate voltage to what you are working on. Are you using a meter or a non-contact voltage tester? I would only use a meter to verify at this point because a non-contact can pick up induced voltages. If you don't know what you are doing, then please call an electrician to straighten this out, it won't cost as much as a trip to hospital.