Actually, the original version was for the soundtrack of the movie Cat People.

Here's the original version (and hopefully the one Tarantino's using?):
http://www.youtube.com/watch?v=0djNOF4g5NQ
http://www.allmusic.com/cg/amg.dll?p=amg&sql=...

I haven't read the original novel version of It, but from the sound of that they could possibly do something similar to the psychic battle at the end of Scanners, where you aren't quite sure what's happening in the physical world and what's psychic until the end.