title: How can I programmatically determine if the Visual C++ Runtime 8.0 is installed?
body: <p>I have an InstallShield installation that uses custom actions that depends on the Visual C++ Runtime 8.0 sp1. In the past, I was able to install the runtime using the merge module provided by Microsoft with Visual Studio. Based on the way the Visual C++ Runtime 8.0 sp1 side-by-side installation works on Vista, the runtime cannot be used until the commit sequence of the installation.</p>
  
  <p>This means that I must either move the executing of my custom actions to the commit sequence (undesirable, since the installation can't be rolled back during this sequence if something goes wrong) or install the Visual C++ Runtime before my installation using an InstallShield prerequisite. </p>
  
  <p>I would prefer to install the Visual C++ Runtime as a prerequisite, but a prerequisite for this is not provided by InstallShield, so I had to write my own. I was able to figure out how to configure the prerequisite to install the runtime, but I don't know how to determine if it is already installed. Is there a registry key or file version I can check to determine this?</p>