Drive image created by PowerQuest disk imaging software; creates an exact copy or "image" of a hard drive used for backup purposes; can be used to restore a hard disk in case it crashes or fails. PQ! files can be opened with PowerQuest's PQIBrowser (PQIBrowser.exe) or Symantec Norton Ghost (part of Norton SystemWorks). PowerQuest was bought by Symantec and rebranded as Norton Ghost; Ghost saves backup files as .GHO files.
File extension is used by PhreeqcI.