First, I am not a Linux guru, I've just tried different Linux distros. So, this distro I would recommend may not work for you. I think it should, but it may not.
I think, from what you're describing, Mint might work for you. It comes with a truck load of codecs and apps in its DVD. (Some legal in the US, some not, be warned.) It also comes with audacity natively (From the DVD, I THINK) so it will PROBABLY do what you want it to. That, and to top it all off, it comes in 64 bit.
Hope this fixes your problem, and if not, please let me know. I'd be glad to help.