It is a good practice to make a copy of the entire Part Catalog directory before you modify anything. If you make any mistakes, you can replace the Part Catalog with your copy. Otherwise, you have to reinstall Autodesk Civil 3D. Make a copy of C:\Documents and Settings\All Users\Application Data\Autodesk\Autodesk Civil 3D <version>\enu\Pipes Catalog and store in a secure place, such as a backup drive or disc.