If you want to record streaming audio, you can't go wrong with
WM Recorder - it's able to record Windows Media Player files, Real Player files, even a bunch of flash (rtmp, flv) type files as well. Alternatively, you can also use
Replay A/V - which can record directly from most audio sites AND has a 'record what you hear' feature that records the sound coming out of the speakers.
If you want to record the audio from a CD on your PC - you should check out
Replay Music which was made just for this sort of thing.
Try em all (free demo) and see which one bets suits your needs.
Let me know if you have any questions, I use them all and love them all as well.
MG