Microsoft is blocking its ability to ensure compatibility:
They have actually placed a hard block on the device drivers for the time being, to stop the virtual drives from loading. It is more than likely in place to help them beta test Vista without having reports from beta users regarding virtual drives, which might complicate things. We are working with them at the moment to ensure there are no incompatibility problems in the future.
As a result, “As of this time Alcohol 120% will not work in Windows Vista Beta, although we do hope to support it once we get past the RC1 release and further,” Alcohol Soft says.
Roxio and Nero cannot be definite about the compatibility of their product either.
Roxio says that EMC Version 9 is Vista compatible, but Vista is a moving target, so we can’t assure 100% compatibility until after Vista is final and released. We may have to release an update at that time, but we are committed to doing so if necessary.
Nero is “currently working on” reliable compatibility but could not commit to anything more definite “at this stage”.
However, Vista RC1 users report that Deep Burner (shareware) and ImgBurn (donation-ware) are working.