If you mean StarTrek you could try extracting from a StarTrek DVD, or a Futurama DVD, I have noticed that they have "borrowed" a lot of sound effects from Startrek!
The BBC used to have a massive sound effect archive, though I don't know if they have any StarTrek ones though.
If you mean the new "Enterprise" show, find someone with a HD or DVD recorder and get a copy from a show they have recorded, from a satellite rather than terrestrial as the are broadcast digitally.