You *MUST* install DirectX 9.0c that is part of the installation. Direct X is a side-by-side versioned system. Each DirectX version is totaly imcompatible and non-backward inclusive.
In other words, no DirectX update will ever overwrite or replace, or take the place of any that have gone before. This means 3d programers don't have to worry about someone changing the run-time 3d graphics out from under them.
Each version of DirectX installed runs in parallel with all the others on the computer, without interfearing with each other.
The setup spawns to DirectX installer if you don't have a compatible version of DirectX installed. When you cancel the install, and then try to run WorldWide Telescope, since the code we depend on to run is not installed there is *NOTHING* the program can
do at that point to warn you of why since Windows does not have the nessesary files to even complete loading our code.
If you just run the dxsetup.exe in the program files directory, or re-install and select repair, you will be running in a few minutes.
Jonathan