I've done a lot of research It seems, but nothing is working. I recently bought the 707/727 from Captain Sim, but when setting up, it asked me to 'Select the Location of Microsoft Flight Sim' but the button is gray?

PanAmerican1957 wrote on Jul 29^th, 2023 at 10:04am:

The 707 is only for FSX/FSX-SE, while the 727 is for FSX, FSX-SE, and P3Dv3/v4/v5 (should be fine to install in P3Dv6 too). It won't work in MSFS 2020!

So... To install it in Microsoft Flight Simulator X (Steam Edition), you need to click on the Browse button, locate the C:\Steam\steamapps\common\FSX folder and click on it. The 707/727 should install there without any problems.

Note. If Microsoft Flight Simulator X (Steam Edition) isn't installed in the main Steam directory, then you will find it in X\SteamLibrary\steamapps\common\FSX (where X: is the drive where the SteamLibrary folder is located)
i.e. on my PC, FSX-SE is installed in E:\SteamLibrary\steamapps\common\FSX, so that's the location I need to select to install Captain Sim FSX products in FSX-SE.

Yeah. My bad. Looking at the intsallation files I have for the 727, it's only available for FSX/FSX-SE, and a different installer for P3Dv3. I probably did confuse it with the 737. Sorry.

I tried installing the 727 in P3Dv4, but due to the fact that the aircraft is made for the 32bit flight sims it didn't work in the 64bit flight sim.