The obnoxious bug in XP that causes Explorer to read the entire contents of broken AVI files before allowing any access to them is caused by bad behavior of shmedia.dll. This problem manifests itself by causing Explorer to read the entire contents of an AVI file, regarless of its size or location any time the mouse pointer is hovered over it, or an attempt is made to access it in windows explorer. This causes 'permission denied' errors when trying to simply move, copy or delete these files as they cannot be changed while Explorer has an open handle on them. This also causes a DoS situation where large AVI's are stored on remote shares and Explorer keeps reading the files from beginning to end each time they are accessed. To correct this misbehavior in Windows XP, remove the following registry key. HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{87D62D94-71B3-4b9a-9489-5FE6850DC73E}\InProcServer32 This will prevent Explorer from loading shmedia.dll in response to file property queries on these files. This will not effect your ability to play files, get file attributes, or even view thumbnails. Say goodbye to all explorer.exe 100% CPU issues.