FastStone Image Viewer keeps its history at "C:\Documents and Settings\<username>\Application Data\FastStone\FSIV\HisFolderList.db". Whilst it would be nice for CCleaner to clober this automatically, even if I put it in the "Custom Files to Clean" list, CCleaner resolutely refuses to delete it.
Deleting it manually presents no problem, so there's no permissions issue or the like.