What causes icon corruption in Windows 7?

I don't know what causes icon corruption.

To rebuild the icon cache:

  • Enable Show hidden files and folders.
  • Open My Computer
  • Navigate to %systemdrive%\Users\"your User Name"\AppData\Local
  • Look for IconCache.db and delete it permanently (holding the Shift)
  • Reboot the system.

Reasons of Corruption are Obscure until now..
You may have to Rebuild the Icon Cache in Windows 7

Information

If one or more of your icons are not displaying correctly, or that your icon cache is corrupted, then you might consider rebuilding the icon cache to reset and reload the icon images into the icon cache.

Note
This will not help with any of the following icon issues:

1-A shortcut's icon that is not displayed properly due to the source
of the shortcut being moved or deleted. You may need to recreate a new shortcut directly from the source (ex: program's exe) file to replace it instead.
2- All icons for a specific file extension display the wrong icon. This may be do to setting the wrong association for what program to open the file extension instead. You can restore the default file extension's associations to fix this icon instead.

If you have check that the source icon is not corrupted use this solution:
Windows 7 - Icon Cache - Rebuild from the SevenForum tutorials