Sony Acid 5.0 feature help Options

[Event]

my friend has been having trouble with a feature on Acid 5.0

let's say he put together a track that's 1 minute long. if he clicked to add a new sample around the 30 second mark, everything after that mark would shift over. the sample wouldnt be allowed to be created along with the existing tracks.

i hope this makes sense. it's kind of like inserting a picture into an essay in microsoft word, "in line with text" vs "in front of text"

whats the feature thats causing this?