Yup all the points that you highlighted are right GrantSP, i having all those issues, so i will put some images that hopefully will help solve this. https://oi59.tinypic.com/34ig36e.jpg - Here is my parameters for the diretory of G.E.C.K. and Mod Organizer. https://oi61.tinypic.com/2pphrgi.jpg - Then i have created a Vault74.esp and did not activated on the Load order, and this .esp is on the overwrite folder. https://oi61.tinypic.com/28tj9xi.jpg - Ok, in this part i have selected the .esp alone, and opened, did some cellcopy and created a simple vhallway, then i try to save as a vault74.esp and say that the same .esp is select or it is a master, i have this part is a little confused to me, so a created a vault74a.esp and saved. https://oi59.tinypic.com/os7ear.jpg - at this point i have 2 .esp files in the overwrite folder, so i created a mod folder to allocated the mod (Just a to be clear, i have the vault74.esp on the overwrite remove and renamed the vault74a.esp in other tests, and the problem persisted), then have the vault74a.esp renamed and placed there. https://oi59.tinypic.com/fx3yte.jpg - So i opened the file again, and made some changes on the render, add some other parts, and saved the same way, renaming it, but when i opened again this massage shows up, i clicked yes and continued. https://oi61.tinypic.com/15hk0hz.jpg - And this is what gave me some rage time, the only part that saved was the curve and the exit of the hallway, the only two things that i changed in the other file. I really don't know what i did wrong, or is a problem with the way that MO manage the files of G.E.C.K. or i did something really, really wrong when i had saved the file or managed, i do really hope that i wrong in this matter so i can learn something from all this, anyway i hope the images could clarify my problems. Ps: sorry for my english is a little dull, and my way of manage the forum topics, i still new in this.