Security Update for .NET Framework 4 Windows Update error. Here’s how to fix.
Since this morning I’ve been getting a Windows Update error when trying to install KB2160841 on my Vista 64 machine. Restarting the PC has had no effect and the small Windows Update icon has been popping up constantly. I couldn’t find any help on Google at all but I did finally manage to fix it. Here’s how:
Problem update: Security Update for .NET Framework 4 on Windows XP, Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008, Windows Server 2008 R2 for x64-based Systems (KB2160841)
Fix:
Go to Start/Control Panel
Click Programs and Features (choose ‘classic view’ if you can’t see it)
From the list of programs click on Microsoft .NET Framework 4 Client Profile and then select Uninstall/Change (at the top).
A small window will pop up. Select the ‘repair’ option and click ‘next’. This may take some time, it appeared to freeze for 30 seconds for me, but soon you’ll see the green progress bars slowly repairing your system.
One that’s done you’ll need to head back to Windows Update so click Start/All Programs/Windows Update and select ‘check for updates’.
That annoying .Net security update will appear but this time it will install as expected so go ahead and install it. Ta da!

Thank you!!! It worked for me just awesome!..