My earlier post Incorrect icon shown for a file type in Vista (March 31, 2008) tells you how to refresh the shell icons in Vista. In case the solution posted in that link does not help, you may want to clear the icon cache database. The icon cache can be cleared by deleting the hidden file named IconCache.db in the following location:
Note: %userprofile% represents the path to user profile folder.
Rebuilding the Icon Cache Database
1. Close all folder windows that are currently open.
2. Launch Task Manager using the CTRL+SHIFT+ESC key sequence, or by running taskmgr.exe.
3. In the Process tab, right-click on the Explorer.exe process and select End Process.
4. Click the End process button when asked for confirmation.
5. From the File menu of Task Manager, select New Task (Run…)
6. Type CMD.EXE, and click OK
7. In the Command Prompt window, type the commands one by one and press ENTER after each command:
CD /d %userprofile%\AppData\Local
DEL IconCache.db /a
8. In Task Manager, click File, select New Task (Run…)
9. Type EXPLORER.EXE, and click OK.