AutoPlay weirdness on removable drive with Macrium image on it (Win 7)

Windows 7 AutoPlay doesn't automatically open an Explorer window when I plug in a removable drive with a Macrium image file on it. I get a general options dialog with options, but no tick box to check which says "Always do this." It doesn't matter what other files are on the drive, if there's a Macrium image it does it. Without a Macrium image it's okay. It opens fine on Vista and XP though. I set every option I could in AutoPlay to "Open folders to view files" but no good. Anyone else ever come across this in Windows 7?