AutoCAD DesignCenter (ADC), command-line, Object Properties (OPM), palettes and other AutoCAD dockable windows may disappear - get out of your current screen (e.g. after you change your display resolution) and it may be difficult to get them back.
You can change/reset the coordinates of the individual AutoCAD child windows in the FixedProfile.aws XML file. (You can make a copy of it, rename it to FixedProfile.xml and display it in MS Internet Explorer for better legibility.)
This settings file is stored in e.g. (depends on the product name and version):
C:\Documents and Settings\{username}\Application Data\Autodesk\Autodesk Architectural Desktop 2004\R16.0\enu\Support\Profiles
You can carefully edit this file using Notepad or just delete in (keeping a backup copy) and AutoCAD will recreate it with default settings in its next session. You can then compare the backup copy with the newly created version and perform necessary changes in your original aws file.