When you open the Options Dialog, the first Tab, moving from left to right, is the Files section.
Support File Search Path
First and foremost is where AutoCAD will look for support files that it needs to get the job done. You can get into trouble by adding too many or not adding enough to this list. Click on the little plus sign to see what is already in place.
Out of the box, AutoCAD has the base folder paths that are needed to keep AutoCAD running. To add additional paths just hit the Add button on the right and Browsing until you find the desired directories.
Things to include may be the location of your Standard Blocks, Linestyle, Fonts, etc.
TIP: Remember that the order of the list matters (notice the Move Up and Move Down buttons). AutoCAD looks in the folders from top to bottom and stops looking once it has found a file by the name requested.
Working Support File Search Path
This section is read-only. This is what AutoCAD actually found from the lists above. If your server is down or someone has moved a folder or you have un-docked your laptop, then AutoCAD may not find some of the critical folders you have added above. When you reconnect and restart AutoCAD, the folders will be resolved.
Device Driver File Search Path
Device drivers for your input device, printer, plotter and video display, etc. must be stored in this folder for AutoCAD to find and use them. Again if you have multiple folders it will use the first one it finds.
Warning: Even though it looks like you could remove it – do not remove any standard folders that are set. Do not remove the DRV folder that is there.
Project Files Search Path
The Support folders outlined above are used for every file that you open. If you want to have additional folder searches based on the project you are working on then you need to add them to this area.
This setting is for resolving XREF, Image files and DWF Underlays . Each project can searches different directories. It’s a simple process of Adding a named project and then adding the directories you want AutoCAD to use. Once you have added these optional paths you need to tell the DWG file to use them.
The PROJECTNAME system variable stores the project name. The project name corresponds to a search path for external reference (xref) files associated with the project. You can create any number of project names with associated folders, but each drawing can have only one PROJECTNAME variable set.
This can be done when an xref or image is not found in its original path. The project name points to a section in the registry that can contain one or more search paths for each project name defined.
Project names make it easier for users to manage xrefs and images when drawings are exchanged between customers, or if users have different drive mappings to the same location on a server. Even better than this is to use Relative Paths for Xrefs.
If the XREF or image is not found at the original path, the project paths associated with the project name are searched. If the xref or image is not found there, the AutoCAD search path is searched.
TIP: don’t forget that the PROJECTNAME variable is stored in each drawing file. If another machine does not have the Project Search set, they will not see the XREFs. If a file does not have the variable set it never looks in this area.