Managing External References - AutoCAD 2011 and AutoCAD LT 2011: No Experience Required - page 692

Setting the Xref Path
When you attach an xref to the host drawing, AutoCAD stores the name of the
xref and its path.
Each time you open the host drawing, AutoCAD searches for any xrefs saved with
the host file and displays them in the host drawing. If the xref drawing is moved to
a new folder after the xref has been attached to a host, AutoCAD won't be able
to find the xref and can't display it. To avoid that situation, you must update the
host drawing with the new path to the xref file. Let's go through a quick exercise
to illustrate how this works:
1. Use Windows Explorer to create a new subfolder called Xref within the
Training Data folder you previously set up. Move 13C-SPLAY1.dwg to
this folder.
2. Return to AutoCAD, and open 13A-FPLAY3.dwg again.
The xref doesn't show up, and the References—Unresolved Reference
Files dialog box opens (see Figure 13.34).
FiGuRE 13.34 References—Unresolved Reference Files dialog box
AutoCAD is unable to find the xref because the path has changed.
3. Click the Update The Location Of The Referenced Files option to open
the External References palette.