Indeed the registry is the way to go. Here is a post on LAVA I did a while ago where I use AutoIt to get the different versions of LabVIEW installed (development or just RTE) and then run the appropriate version for the one installed.
http://lavag.org/topic/17803-run-exe-based-on-installed-run-time/
The source code is included so you should be able to understand the registry keys I read to find the versions installed.