When using many of the functions in spatial analyst, the grids that are created and that appear on your View are only temporary. You will know this is the case when, for example if you use the Derive Slope function, you are not asked to name a file and to specify a location for it. It simply runs the process and loads up a new grid for slope. This is because many grids are intermediate steps to a final data set. As long as you don't save the Project, these grids will be deleted from the computer when you exit ArcView. If you so save the project with the temporary grids on the View, they will be saved, but in a location and under a name that are unknown to you, and so are quite useless.
To see where a temporary grid is located and what it is called, make that grid the active theme and choose Theme-Properties. This will show you both its theme name as it appears in the Legend and its real source name and location in your computer (typically c:\temp or e:\temp).
For each grid that you ant to save as a permanent grid, write down the source name and location.
Before you do anything else, create a new folder in your project folder specifically for the new permanent grid data sets (e.g., e:\temp\waller_creek\final_grids\
Under the File menu, there is an option for Manage Data Sources. This allows you to delete, copy, and rename data sources such as shapefiles, grids, and TINs. Because each of these data sources is made up of multiple files (plus an INFO folder if dealing with a grid or TIN), make sure you use this utility to perform these tasks - don't use your computer's file system commands.
By default, Manage Data Sources lets you delete, copy, and rename shapefiles. If the Spatial Analyst extension is loaded, you can also manage grids. Just change the Source Type to Grid. If the 3D Analyst extension is loaded, you can also manage TINs. Just change the Source Type to TIN. Choose a data source from the list on the left, then click the button for the action you wish to perform.
Copy -You'll be prompted to enter the new name and location for the copy of the data source - use this option to create a permanent new data set in a location of your choice.
Rename - You'll be prompted to enter the new name for the data source.
Delete - You'll be prompted to see if you really want to delete the data source.
Copy only the grids that you will need to have on a permanent basis (e.g., the elevation grid in the new coordinate system, and the final slope and aspect grids).
Once you have copied them to a new location, add the new permanent grids to your view to make sure they copied properly.
If they appear correctly, then delete the temporary grids from your view, and save the project file under a new name.
To save space on the local computer, please delete (again using File-Manage Data Sources) all the temporary grids.