This replaces the GLaDOS voice in the GLaDOS voice map included in the Portal: Still Alive for PC mod. This is not intended for the base game but rather the sourcemod.
This is an addon intended for Portal: Still Alive PC, however, I am unable to post addons for that mod, so I have to post it here. I suggest downloading the sourcemod if you don't currently have it: Moddb.com
To install, extract to:
(or whatever your directory for the still alive mod is)
It will ask you if you would like to replace the "GladosVoiceMap.vpk" file already in the mod, make sure to click yes. Once you've done this you should be good to go. Start up the mod and play the map. Enjoy these more accurate GLaDOS voice-lines! :)