The preview feature in Windows Explorer is really useful until you need to perform file management tasks on AVI files like deleting, renaming, or moving them. You’ll often get “access denied” messages if you don’t let Windows finish its scan. So to remove this feature, you can run these commands from a Command Prompt (Start -> Run, type in ‘cmd’ hit enter) to remove image and media preview:

regsvr32 /u shimgvw.dll
regsvr32 /u shmedia.dll

And if you decide that you need to re-enable image and media preview, use these commands:

regsvr32 shimgvw.dll
regsvr32 shmedia.dll