Thanks for your response.
I'm sorry I didn't give enough details of what I wanted to do. Well, I just got an audio session from a singer, and she wants me to remix her track.
I got the project with all audio tracks, but I found out that the guys from the studio she recorded with probably exported these as new audio tracks and forgot to select the "keep original file" option or something, and now I can't manipulate the tempo of the session. You know, in order to do the remix I need to change to a faster tempo. I already tried different things, I did what you suggested before (trying to convert these regions into audio loops), but still they don't get affected by tempo changes, so I don't have any idea of what else I can do. If you guys come up with any possible solution, please let me know. That'd be great.