There seems to be an issue with installed font files that contain the character U+FFFD Replacement Character. For those files, CCleaner incorrectly reports the font files as missing.
To reproduce (Windows XP):
1. Download a font file. Put the character U+FFFD in the file name; one way to do this is to hold “Alt” and press “+fffd” (use the plus sign on the keypad), though I believe that you need a certain registry setting to be able to input characters via hexadecimal.
2. Install the font file.
3. Open the Control Panel > Fonts folder.
4. Run CCleaner.
5. You get an “error” about how the font file, referenced in a registry entry and containing the U+FFFD character in the file name, cannot be found. The U+FFFD character is represented as a Question Mark character in the error message.
6. Delete the registry entry indicated in the “error”.
7. Reopen the Control Panel > Fonts folder.
8. Run CCleaner. The “error” is back.
(Note: I didn’t follow steps 1 through 3 since I already had installed the font. Step 3 may be unnecessary.)
What should be happening:
No error should be reported. The file exists, but it seems that CCleaner can’t handle the U+FFFD character.
You might ask why this character would be in a file name at all. I use it as a substitute for characters that Windows won’t allow in file names, such as the question mark or slash characters.