Unfortunately, the free and cheap Kontakt libraries won't work with the Kontakt Player. Any libraries that work in the free player have to be licensed with Native Instruments, who demands very high fees which greatly inflate the price of the libraries. You might want to think about getting the full Kontakt, which will expand your options - including making your own libraries, which is fun.
I remember looking at the Olympus Micro Choir last year when it was released. It generated a lot of buzz at the time, because the SoundIron choirs are among the best there is. The buzz died down quickly when people realized how limited the library really was: it sang one word - "dominum". Sang it beautifully, though. By carefully adjusting the attack and offset controls you could extract the syllables from "dominum" and get "do", "oh" and "ooh". I passed on it. Even at 10 bucks I couldn't see I'd ever use it. The new version apparently adds a chant, some Russian word.
At any rate, you won't be able to use it without full Kontakt, as is the case with all the inexpensive libraries.