On a RES workstation, file associations can be problematic. RES does not really like the existence of alternatives, and for some extensions, such as .pdf and .ps, RES has already decided for you which program should open such files. If you have access to WinEdt or Scientific Workplace, RES may also have preempted the .tex extension.
TeX Live offers several editors: TeXworks because it is part of upstream TeX Live, TeXstudio because it is more suitable for new users, and TeXnicCenter for historical reasons: it still works well for many old-time users, and I rather not force anybody to change their favorite editor. A final option is selecting your own.
The TeX Live launcher has a button for selecting your preferred LaTeX editor. This appears to work ok on a physical workstation, at least for the running session.
With the latest update of the remote UWP (the Windows 10 lookalike), double-clicking a.tex file in a file manager such as Windows Explorer resulted for me in the following popup window:
If that happens, and if the desired program shows up, just click the desired item. Hopefully it sticks until the end of your session. If you do not see the TeX Live-supplied program, you can either re-initialize TeX Live (Tools menu) or open the program from the launcher.
You can also right-click your file:
But here, too, the desired program may be missing.
All in all, I consider the handling of file associations in RES very unfortunate. There are many legitimate reasons for preferring one program above another in a particular situation.
As to editors: people invest a lot in learning to use an editor to maximum advantage and as a consequence get very attached to them.
As to pdf viewers, which is another problem case, Adobe Reader is very much not the right tool for the edit-compile-preview cycle, as explained elsewhere in these pages, no matter how excellent it may be in other respects. At least, the built-in editors use either their built-in pdf viewer or SumatraPDF.
RuG TeX pages last revised on December 8 2016