Should these questions be on-topic for this site, or should they be moved to Super User?
I think as a matter of practicality, the people who are qualified to answer these questions will be in greater abundance here than there. As such, assuming it's on topic on both sites, here is probably the better place.
As for whether it is on topic here, I'm all for including it for now. Maybe it doesn't formally match the proposal description, but these sorts of things should be ironed out during the private beta, rather than just following the description. If we find that these questions are overwhelming the more directly relevant ones we can remove them, but I think they are likely to be uncommon and will be a good reference for those who use the site provided that they stay that way.
Questions like this are more about the process of extracting text from a compressed video file. These are not questions unique to the anime/visual novel medium (they could apply to other types of files that fit the same parameters) and are thus off-topic.
Super User is a good choice. Also consider Digital Signal Processing.
By extension, this applies to questions asking how to extract subtitles from a compressed file.
I'm inclined against the question being on topic. It is entirely a technical question, and does not involve plots/themes/trivia of the medium at all.
The relevant variables in this question are:
- Operating System
- Applocale or base locale switching?
- Full Japanese OS or just Japanese Language package?
- Game platform (which technology base is the Visual Novel using)
... all but the last are utterly irrelevant to this site.
The analogous question to this one over on movies would be "How do I digitize my Betamax movie collection?". Although it's true that movie-buffs are more likely to have an answer, it's also offtopic.
With that said, if we create an 'enhanced FAQ' entry that specifies whether Visual Novel questions themselves are on/offtopic, I think it would be good for that FAQ item to include the answer to this particular question as a snippet. (I'm also contemplating adding it to the resources FAQ over on the Japanese language site.)
EDIT: I think those who support this question as ontopic need to explain whether "I can't play Episode X of anime Y from group Z, help!" is ontopic or not. Or heck, even "Why can't I play Visual Novel X?" These are just examples of other technical questions that are peripherally related to anime... that anime fans are most likely to have the solutions for.