On Windows 7 the AIR runtime seems to be installed here:
C:\Program Files (x86)\Common Files\Adobe AIR\Versions\1.0
Even though it says Versions/1.0 the Adobe AIR.dll file reports the correct version of 3.9. There's no other subdir in the Version dir.
Thanks I found it. but now I have another problem. When I tried to run setup.msi I get the error: "Could not access network location(computed)" I don't know exactly what this means, but the internet is enabled and Air is not blocked by the firewall.