Not able to record onto Adobe Audition 1.5

Sounds like you do not have your audio recording source set correctly.  If you're recording from a file on your computer or a CD via the CD-Rom drive of your computer, you need to probably set the recording to either "Wave" or "What you hear", one of the two.  The "What you hear" can be easiest, but then again, if any other sound comes accross your computer at the same time, you'll end up recording that as well, so it's best to stick to "wave" if you can... or make sure all Windows sounds are turned off (Audio settings ->Sounds ->Select "No Sounds" as the theme).