CCleaner doesn't support Unicode. You'll have to go into the registry yourself to delete those (Start > Run > regedit). It's probably a corrupted key. Also, it won't look like a few question marks and a square when you get in there, so look carefully. CCleaner can't take you there, because again, it doesn't support Unicode (and it thus cannot read the entries correctly). The entries do exist, but CCleaner can't properly display them - the NT 5 registry is fully Unicode but supports most non-Unicode functions. So, CCleaner is able to see that something is there, but it can't display it properly - instead it splits the Unicode into two separate bytes, and displays ASCII, question marks, or boxes, to replace the characters with a value higher than 255. It also looks like it may have been associated with malware, since it's missing.