The MXD Defragmentor utility defragments the storage inside an ArcMap document (MXD) file to potentially reduce the file size. You'll find this utility useful if your MXD files are large in size.
You can either defragment a single MXD file or all of the MXD files in a particular folder. When you run the MXD Defragmentor, a new MXD file is created in the same folder as the original file. The name of the new MXD file is the same as the original file name with _Defrag appended to it. For example, if you run the defragmentor on JoshuaTreeNP.mxd, the new file will be JoshuaTreeNP_Defrag.mxd.
This utility is provided as is. The MXD Defragmentor writes out a new MXD file instead of modifying the original file; however, it is still good practice to back up the original file before using this utility.
How to use the MXD Defragmentor Utility
The MXD Defragmentor utility is delivered as an ArcMap command. Follow the steps in How to set up the MXD Defragmentor to add this command to ArcMap.
Click the MXD Defragmentor command in ArcMap to display the following dialog box.
1. Choose a file option.
* To defragment a single MXD file, click Single file.
* To defragment all of the MXD files in a particular folder, click Directory.
2. Click Select and navigate to the single MXD file or the folder that contains MXD files.
3. Run the defragmentor.
* If you want to run the defragmentor and automatically dismiss the dialog, click OK.
* If you want to run the defragmentor and leave the dialog box open when the process is finished, click Apply.
4. To dismiss the dialog box, click Cancel.
source : http://edndoc.esri.com/arcobjects/8.3/
