Error Installing KB976462 during SharePoint Pre-Requisites Installer

I was running the SharePoint Pre-Requisites installer this week. Upon competition it failed to install KB976462 and then skipped the rest of the installers. It turns out a second running of the installer then successfully installed the rest of the pre-requisites. I could have just continued on my merry way, but having a weird issue like this hanging out there can usually lead to some very strange issues further along in the install process so I dug in to figure out what was wrong.

The first step was to figure out what the KB was and this lead me to the Microsoft kb article for it:
http://support.microsoft.com/kb/976462. It turns out this is a patch to the .NET framework 3.5 SP1, this seems like a crucial thing to have installed properly. Next I logged into one of the other servers provided to me and checked to see what versions of .NET was installed. In order to determine the .NET versions I navigated to the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\ upon viewing the versions installed in this key I noticed that only version 2 or .NET was installed.

On this other machine I then used the proper method to activate .NET v3.5.1 by adding the windows feature from the server management console. After the feature was activated windows update was run to make sure that all of the current patches for .NET were downloaded and installed. After the feature was activated and windows update was run the pre-requisite installer was executed and it ran without any errors.

To be on the safe side I had the first server rebuilt because installing SharePoint on a server with an improperly installed .NET v3.5.1 did not seem like a good path to go down.