Hi Workaholic, that's what I downloaded from this page (Directory Opus 12.10). I was expecting it to be an 12.10 installer, but it turned out (I think) to be 12.11. In fact, I just checked and the download url on both the page for 12.11 and 12.10 are the same, so I guess they always point to the latest version. Hmm. I'm not sure what's going on. Anyway, I initially downloaded 12.11 via "Check for update", so that could be where I got the file with the unchecked compatibiliy box from.
Anyway, re: (2), yes absolutely, one of the two files came with the compatbility boxes checked. That's the one that ended up installing.
Re: (3), on my machine at least, I've never succeeded in installing dopus without having the compatibility checkbox checked. I should also clarify that, although I installed dopus in compatibility mode, it (dopus.exe) does not run in compatibility mode. The app runs just fine after installation.
Re: (4), no, I have not had that problem. It's always "Program Files" and not the other one.