source:
Microsoft KnowledgeBase
[*]Start Registry Editor (Regedt32.exe).
[*]Locate and then click the Default value under the following keys in the registry if this problem occurs with folders:
HKEY_CLASSES_ROOT\Directory\shell
If this problem occurs with drives:
HKEY_CLASSES_ROOT\Drive\shell
[*]Click Modify on the Edit menu.
[*]Type none in the Value data box, and then click OK.
[*]Quit Registry Editor.
P.S., 顺便说一下怎么找着的。到google,打double click open search, 搜索,第三条结果直接就是MSKB