Stop Quicktime .MPEG playback in Vista?

Since updating my Internet explorer to the latest version of 9 all streaming .MPEG videos have stopped opening in Windows Media Player and instead now open inside the browser window through Quicktime. I have tried every fix I could find including changing the MIME settings through Quicktime and the default file types for Windows Media Player. Nothing seems to work and it's driving me absolutely insane, someone please help!