If the folders you refer to are on the Desktop it may have been caused by restoring to an earlier date or time. If not on the Desktop restoring wouldn't have caused it or so I understand (but as finicky as Windows can be, who knows). A Windows ghost has done this to me a few times with no [appear ant] cause. Perhaps assigning a Read Only attribute to the files may help prevent it.
You may be able to correct it using System Restore or right clicking on the folder > left click Properties > left click on the Customize tab and
''Choose Picture'', ''Restore Default'' or Change icon''.
Hope this helps.
The My Music, My Pictures and My Videos folders have all lost their icons and just have the normal folder icon. Does anybody know how to get them back and stop it happening again?