There was a thread a long time ago (a year or so) about cleaning up the libraries in B4 and I think the same applies to B5. When you delete an object, mat, etc from your libraries, only the icon disappears. B4 library still remains the same. As I recall, and backup before you do this, the method of cleaning the library is simple.... 1. Delete the ones you don't want. 2. Select all in the library and export the entire selection as an .obp or .mat as appropriate. 3. Notice that the exported file is smaller than the library you were in. 4. rename the export to the exact same name as the library you were working in and copy it back overwriting the original (or better yet, move your original to a temp directory and bring in the renamed one). 5. Double check that when you go back to Bryce your presets show up with all the ones you selected. 6. Do this for all your libraries.