We have several congregations using the same computer, how do we separate the recordings?
Create a user for each congregation, all settings are individual for each user so the recordings will be saved in their home document folder.
The recordings are very low or are very distorted, how come?
This usually is dependant on incompatibilities between the computers soundcard and the mixers inputs/outputs. It could be quite hard to get a good setup here, if you have the possibilities try different combinations and also try different inputs on your soundcard and choose the one with the best sound.
Why is there a humming sound when we connect the computer to the mixer?
This is due to ground loop currents, computers are not built for connecting to a PA system and will often cause these problems. There are several ground loop isolators available on the market, so do a search at e-bay or try your nearest HIFI store (the ones working with car stereos) and buy 2 isolators (1 for input and 1 for output.)