When you open or save files in various applications that use the Common Dialog control, the recent file names are stored in the registry. If you click the arrow in the File name box in the Open dialog box or the Save As dialog box, a list of the files that you most recently used appears.
This article explains how to clear the recently opened files listing in the Command Dialog boxes.
The above method erases recent documents history, file names MRU in Open/Save As dialogs, the MRU entries in the Run dialog (RunMRU), and the typed URLs history (TypedURLs) in Internet Explorer. If you want to selectively clear the Common Dialog file names MRU, you need to delete these two registry keys manually:
HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ ComDlg32 \ LastVisitedPidlMRU
HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ ComDlg32 \ OpenSavePidlMRU