This file was mistakenly left out of the Premiere Pro CS5 installer for Windows, so people who tried to switch to this keyboard shortcut set were unable to do so.
Unzip the file and then install the .kys file by copying it here:
C:\Program Files\Adobe\Adobe Premiere Pro CS5\Keyboard Shortcuts\en_US
(where C may be replaced by the a different drive name if you installed somewhere other than the C drive, and en_US may be replaced by another locale ID)
This file was included in the Premiere Pro CS5.5 installer, so manually installing this file is only necessary for Premiere Pro CS5 for Windows.
For information about keyboard shortcuts, including how to customize them, see this page: