1. Delete "sound" file inside your 737 folder.
2. Copy and paste the "sound" folder that came in the "737NG CFM56-7B" zip file.
INSTALATION 2:
1. Delete the contents inside your 737 "sound" folder.
2. Copy and paste the contents of the "sound" folder from the zip file "737NG CFM56-7B".(The one you downloaded)