Today I was trying to install the Parallel Extensions to .NET Framework 3.5 December CTP from MS site (http://www.microsoft.com/downloads/details.aspx?FamilyID=e848dc1d-5be3-4941-8705-024bc7f180ba&displaylang=en). I received an error as I did not install couple of required Windows Updates. I used the Windows Update applet (found in Control panel) to view all the required updates and install them.
If all the required updates are installed then the tool shows a green tick icon, otherwise it shows a red cross icon. clicking on ‘View available updates’ shows the detail of every update and whether it’d required or optional –