When looking for raster files with Windows Explorer, in some cases the associated auxiliary (.aux) and pyramid (.rrd) files are not appearing in the same location as the raster itself, as they should.
In ArcGIS 8.1 the libraries used to determine the read-only status of the raster, or the folder containing a raster, don't analyze administrator permissions. Any form of read-only permission or security setting renders the raster as read-only, this requires the use of proxy files. Depending on permission settings, the file browser may still be able to write to the raster folder.
See the online help on proxy files. These are files created when read-only rasters are encountered and there is a need to store additional information about the raster dataset. ArcGIS writes these files to a separate location, the raster proxy folder.
Eliminate all forms of read-only/security permissions. This will allow the .aux and .rrd files to be written next to the raster. Remember to manually delete any previously generated and unneeded proxy files; use the file browser for this.