Many ways to go by that. A whitepaper discusses how to extend the Application Runtimes view:
http://www.installaware.com/installawar ... s_view.pdf
But you don't need to extend that view just to install that prereq. If you want to add a prereq to your setup, you can just follow these simple steps:
1) Download the native prereq installer
2) Process it with the Setup Decompressor
3) Add it to your setup as a Support File if it is a single file. If its multiple files and folders, add it to your setup using the File Bag plug-in.
4) Detect the presence/absence of the prereq using the Read Registry, Check Process, Check Service, Is MSI Setup Installed commands (whichever ones work for you).
5) If absent, install the prereq using the Run Program, Run Program As, or (Un)Install MSI Setup commands (again, whichever one works for you).
That's the basic idea. You can just switch to your setup script and expand the code regions that install the remainder of your runtimes to see how the script flows for installing runtimes, and just copy-paste the code and modify it as necessary.