When opening PACX, you receive an error box stating that there was an error initializing the XAudio2 sound engine and your PACXsounds do not work.
This can be resolved by installing or repairing DirectX with this file.
A specific version of the DirectX libraries is required to play audio from PACX. In some cases, a system has DirectX, but not the right version. Repairing it with the above executable ensures that the DirectX libraries PACX needs are present.