Here is the *real* answer to this question that everyone is looking for:

Missing sku1a1.cab file

1) Get your OneNote product key off your computer.

There is a little free program that will do this for you here:

http://www.nirsoft.net/utils/produkey.zip

2) Uninstall OneNote

3) Download the trial version of OneNote here:

http://www.microsoft.com/office/onen...rialoffer.mspx

4) Install the trial version and enter your product key when prompted

5) Check "install updates" at the end of the installation process and it will install SP2 and put you back where you were before the sku1a1.cab file disappeared.