Save
Saves any changes you've made to the current Active file. If you haven't specified an active file in the Data window, you will be prompted for a new filename to save your changes to.
All changes will be saved to a plug-in file (FILENAME.esp) based on the current master file (Oblivion.esm).
Note: Plugin files cannot contain any reserved characters, such as "(" or ")", or when attempting to select them the Oblivion loader will not recognize them as valid plugins. To remove this error, simply rename the plugin to not contain reserved characters.