From your message, it seems you are installing using old installers, the ones with the sim icons (greyed or not), which would install automatically into the sim.
They surely worked and, if they didn't, it's likely you have a problem with your registry settings. The most common issue is to have FSX:SE installed when FSX was present, then having removed FSX.
However, it's best if you use the current installers, which will NOT install "into" the sim anymore, but in their own folder, so you won't have to install twice or more times, if you have more than one supported sim installed.
If you still have greyed options (they are not icons anymore) with the current installers, then it's sure you have a problem with your registry, which we can then find out.