It sounds like you have been creating all of your projects under one folder. This would result in different .cpr files sharing the same Audio folder, which can be very confusing, particularly if you name tracks similar names (guitar, vocal, bass, etc).
Typically, it is best to create a new folder for each new project. This will create a dedicated audio (and Edits, Images, Freeze, etc) folder within that project folder, which will keep all of the audio files for that project.
If you are looking for a reliable way to remove the undesired audio files, I would suggest first opening each project you want to keep, going to File, Backup, and saving them to a new location. This will copy the audio files for that project. Again, make a new folder for each new song. Also, be sure to backup all of these files to an alternate drive.
Then, when you have verified that you have moved all of the desired projects and they are working properly, you can decide if you want to delete the originals from that folder. I hope this information is helpful.