hooked up my mixer to the computer
Which mixer? I need enough information to dig for info on the connections and how they work.
How new is the mixer? Days, or have you been using it for several years and it's an old friend?
Which Windows?
Neither Audacity nor Behringer changes volume levels like that in normal operation. However, Windows is notorious for hiding little settings here and there. The Systems Office at work gave me a Windows machine to check for sound because it was going into a classroom. I couldn't get it to pass simple sound quality no matter what I did. Turns out Windows had "Cathedral Sound" effects running on a sound panel I'd never seen before.
Do you use Skype or other communications or conferencing service or software? Do you leave it napping instead of completely closing?
I know you don't have this problem, but this is somewhere else to look.
http://manual.audacityteam.org/o/man/fa ... hancements
I guess it should give you a warm-fuzzy feeling to know you have the exact opposite problem from most people.
"My recording is really quiet and noisy when I boost it. How do I fix this?"
Start a normally overloaded recording and turn the mixer off in the middle of a sentence. Just pop the power button and keep talking until it completely dies. Make sure you don't have live monitoring speakers running when you do this.
Koz