or Group Policy or looking for messages within an application does not prevent these media types from automatically playing on insertion. However one can disable Audio CDs by editing the file type for AudioCD and clicking "Set default". This will remove the Play action as the default for that file type. Alternatively, changing the (Default) entry under the key to "" (a blank string) will accomplish the same thing. The disabling action for Movie DVDs is the same, with "DVD" used in place of "AudioCD". The pertinent Registry settings are shown below along with their defaults in Windows 98SE: HKEY_CLASSES_ROOT\AudioCD\shell (Default) "Play" HKEY_CLASSES_ROOT\AudioCD\shell\play (Default) "&Play" HKEY_CLASSES_ROOT\AudioCD\shell\play\command (Default) "%SystemRoot%\cdplayer.exe /play %1" HKEY_CLASSES_ROOT\DVD\shell (Default) "Play" HKEY_CLASSES_ROOT\DVD\shell\play (Default) "&Play" HKEY_CLASSES_ROOT\DVD\shell\play\command (Default) "%SystemRoot%\system32\dvdplay.exe /play %1" Volumes AutoRun If a file called autorun.inf exists in the root directory of the file system, settings in that file can add to the options presented to the user or affect the view AutoPlay has of the content. Under Windows XP, the existence of this file may affect the process flow – AutoRun can proceed to executing an application directly without user intervention. Under Windows Vista, AutoRun cannot bypass AutoPlay in this way; it can only add to the options presented to the user. The Inf handling section of the AutoRun article details when and whether AutoPlay is invoked. The AutoRun layer initially consults Windows Registry values to decides whether to initiate actions for any particular drive or drive type. If AutoRun has been disabled for the newly discovered volume, then the process halts at that point, effectively disabling AutoPlay for that volume. Content sniffing After AutoRun completes, AutoPlay initiates by doing an examination of the volume for content. This is called content sniffing. AutoPlay decides whether the volume is an Audio CD, movie DVD, a blank recordable medium (a CD-R, CD-RW, DVD+R etc.) or a generic volume which contains files. In the case of a generic volume, AutoPlay starts with the root directory and searches the file system to a depth of four directory levels below the root directory to find file types that fall into certain categories or "content types". If this search takes more than a second or so, a progress dialog shows the scanning process taking place. This dialog can easily be confused with an Explorer copy operation; however, no files are being copied or moved. Content types As far as AutoPlay sniffing is concerned,