Actually, the version used was included with the original soundtrack LP released in 1977 as a 45 RPM insert, it was not included on the first CD issue of that album from Arista, but when Varese Sarabande reissued the reissue of the original album, the disco track was indeed there. I picked up the Varese release in 1995 while on vacation in Gatlinburg, TN.
The other part is taken straight from the soundtrack to Star Trek: The Motion Picture, the Main Title to be precise.
And there you have it!