Default Double-click Actions - Goes To Search

I was recently in "folder options" and then "file types", just going through and changing icons for disk drives and folders, JPG's and whatnot. Anyway, after doing that, I noticed that if I try to double-click on a disk drive it'll go to Search. And if I double-click on a folder it'll go to Clear Read Only Attributes. I've obviously changed the default action associated with a double-click on folders and disk drives, and I know how to change the default actions undertaken by disc drives and folders and everything else when double-clicked. The thing is, when I go into folder options, file types, advanced (after selecting say, disk drive) the option to change the default action to "open" isn't there, for either folders or disk drives. Other options such as Find are present, but nothing else