A recent Windows security update failed to install on my Windows 7 laptop. The Windows sign-off indicated the operating system was installing an update before shutting down, but the patch never installed.
The next time I started the machine, I clicked Start > Windows Update to determine which update was failing. The Windows Update warning message offered a link to "get help with the error," but the link led nowhere useful.
I found the remedy described by Microsoft Support's Srinivas R on the Microsoft Answers site: click Start > Control Panel > Programs and Features, select Microsoft .NET Framework 4 Client Profile, and click Uninstall/Change.
In the Maintenance screen that opens, choose "Repair .NET Framework 4 Client Project to its original state" and click Next. After the repair completes, click Finish. When you return to Windows Update, the .NET security patch should install without a hitch. (Note that on my laptop the update took several minutes to install.)
If the update continues to play hard to get, Microsoft recommends that you uninstall all versions of .NET on the machine and then reinstall all versions. Instructions for this tedious task--which entails not one but two restarts--are provided on the Microsoft Support site.
With luck, it won't come to that.