I've upgraded or repaired my Windows XP installation, but now data is missing from the All Users folder. What caused this to happen, and how can I retrieve this information?

A. Data can disappear from the All Users folder if you've performed an in-place upgrade of XP (i.e., installed XP over an existing XP installation), used the XP installation CD-ROM and selected R to repair the XP installation, or upgraded XP Home Edition to XP Professional Edition. To recover the missing data, you must restore the information from a backup copy.

To prevent this problem from happening in the future, look for and delete a file named undo_guimode.txt. This file is typically in the %windir%system32 folder. The undo_guimode.txt file often appears on systems in which the manufacturer has preinstalled XP. The first time you start such a system, the system often calls a wizard that creates the file.