“Open with” box dislikes you
When you want to open a file by right-clicking it in Explorer and selecting from the menu Open with, you might have the surprise on day that the program you were looking for disappeared from the list of options. If you select Choose program, your program is not to be seen in the very long list of programs that Windows believes you could use. Worse, if you click Browse and manually locate the program file, it will not be added to the long list.
If this last thing happened, than the solution can be easy. Windows keeps a list of programs that you added manually to the long list. This is stored in the registry (see here a description of the Windows registry). The list is kept under HKEY_CURRENT_USER\Software\Classes\Applications\ and each program is listed there under its name (say, audacity.exe or XVI32.exe). For each program, its location is stored under the branch shell\open\command.
The troubles appear when you update the program. Chances are that the name doesn’t change, but the path does. Windows doesn’t spy you, so it doesn’t acknowledge this change of location. Each time you will bring up the long (Choose program) or the short (Open with) list of programs, Windows will see that the outdated location points to nowhere and it will silently discard them. But even you tell upfront that the location changed, Windows will still believe its outdated registry rather what you say.
To solve this problem you will have to fix the aforementioned wrong path. (Again, see here for how to edit the registry.) As usually when working with registry, be careful, backup your data before modifying anything, and, most important, do not proceed unless you fully understand what you are doing.