Audition is meant to be utilized with an actual audio interface and the Realtek inbuilt card doesn't really qualify. That said, it should still run. Just to clarify, you are using Audition 3.0? Your biggest hurdle will be finding a second external hard drive. You need some enclosure with at least an Oxford 924 chipset for a bridgeboard. Anything else may or may not work. The drive speed itself should be 7200rpm. If you are recording to the inbuilt hard drive on the laptop that will account for the majority of your latency and errors.

Audition is marketed and geared for broadcast media (radio/tv/internet news). It WILL run on a computer with no audio interface but the usual caveats apply such as tweaking your computer for audio etc.