http://support.microsoft.com/kb/934548/en-us
On a Windows Vista-based computer, you cannot use keyboard shortcuts
to select more than one item in Windows Explorer
View products that this article applies to.
Article ID : 934548
Last Review : April 24, 2007
Revision : 1.0
SYMPTOMS
On a Windows Vista-based computer, you cannot use keyboard shortcuts
to select more than one item in Windows Explorer. For example, you
cannot use the CTRL+A keyboard shortcut to select all the items in a
Windows Explorer window. Also, you cannot select multiple items in a
Windows Explorer window by holding the SHIFT key or the CTRL key while
you click the items.
RESOLUTION
To resolve this issue, use the Reset Folders command. To use the Reset
Folders command, follow these steps:
1. In the Windows Explorer window where this issue occurs, click
Organize, and then click Folder and Search Options.
2. On the View tab, click Reset Folders.