According to Microsoft Download Page for .NET Framework 3.5 SP1, I should install KB959209 and KB967190 immediately after installing the .NET Framework package:
IMPORTANT: After installing the .NET Framework 3.5 SP1 package (either the bootstrapper or the full package) you should immediately install the update KB959209 to address a set of known application compatibility issues. In addition, on Windows Vista x64 and Windows Server 2008 x64, install the update KB967190 to address a file association issue for XPS documents.
I handle the installation of the .NET Framework in my installer (Inno Setup). So how do I detect if those two hotfixes are installed, so I can decide whether to download them and install them? I don't want to bother the user with unnecessary steps, so as automatic and passive solution as possible is preferred.
I had a similar issue in which I needed to detect if a required KB was installed at install time. My solution was to create a custom EXE that uses DTF - Deployment Tools Foundation to check for the KB, and download and install it in passive mode if it is not installed. You can then call this custom EXE from your install process and it can handle the details of detecting the appropriate Hotfix. The discussion can be found at:
Detect and require a Windows QFE/patch for during installation