Problem is not limited to Vista users, I have the same issue with my XP SP2 system. CCleaner always lists file extensions to be removed from applications that I use most frequently. This version does it and so did the previous one. The explanation of what "UNUSED" means, given in a response to a post by Oldboy, Feb 4, 2006, only confirms, for me, that it isn't recognized as a bug. I don't have an explanation but I am watching this post because I hope you soon get one soon. In the meantime, I will stick with the only resolution I know, NEVER remove them.