If you're using the GOG version, you should use PODHacks (this is not a virus) and install a newer version of nGlide. You can find a better Readme for using PODHacks at the GOG POD forum. Afterwards, SweetFX is installed normally, without renaming any folders. If you want to install Dark POD: The Last of Days, you can either download the SweetFX preset with the "Download preset" button, or download the whole mod through the Mediafire links. SweetFX is included in the packages.