This is a problem caused by an older or uninstalled Quicktime installation which has altered the extension subkey in the Windows registry.
Follow Bryan's instructions here to delete it. Check the attachment to see a picture of exactly what you what to delete.
http://forums.techguy.org/showthread.php?s=&threadid=53760
(And welcome to TSG
Follow Bryan's instructions here to delete it. Check the attachment to see a picture of exactly what you what to delete.
http://forums.techguy.org/showthread.php?s=&threadid=53760
(And welcome to TSG