Hi,
- You may find that the directories: /Library/PreferencePanes and /System/Library/PreferencePanes do not have any files in them at all.
- There should be files in these directories which are of kind "Mac OS X Preference Pane: and end with an extension *.prefPane
With an admin account, check if you can:
- Find them within Time Machine or another backup under the above directories and restore or:
- Check whether they are in the Trash and put them back or:
- Find then on the machine and copy them back to these directories.
See how you go