Whether or not a technical question is on-topic for Arqade can be a tricky question, because there is a fine line between "This is a gaming problem best answered by gamers" and "This is a computer problem bested answered by computer experts" (in which case it belongs on Super User).
The main thing it comes down to is whether or not this is a problem about gaming, faced by gamers, and is best answered by gamers. This includes question like Launching Minecraft lags computer, since the problem is directly related to and caused by a game, and gamers are the best suited users to answering this question (since they've probably faced this issue as well).
Questions which are really computer issues are best answered on our sister site Super User, which is a site for Computer Experts. This would include questions like https://gaming.stackexchange.com/questions/31847/how-do-i-tell-if-my-graphics-card-is-defective, since the question is about computer hardware which is only tangential related to gaming. Due to this it's best answered on our sister site, Super User.
So the key thing to ask yourself when looking at these questions is: Is this question best answered by a gamer, or a computer expert? If it's the former, it usually belongs here, if it's the latter it's probably a better fit for Super User.
With that said, there are certainly inconsistencies with how this rule is applied. Since it's such a fine line between off and on topic for these types of questions it's very difficult to always apply it correctly in every case. Furthermore, since we have such a large number of users, the users who just happen to stumble across a question also play a large factor. For although I may think a question is fine, another user may disagree and vote to close. This is all due to that fine line I mentioned earlier.
Finally, there are cases where a question just fell through the cracks, or was overlooked after a change in policy. Your best bet when you stumble across these types of questions and you're just not sure if they're on-topic is to either:
- Flag the question to draw the attention of mods and 10k+ users
- Leave a comment
- Hop on over to our chat and ask what the users there think. Our chat is fairly active, and you'd be hard pressed to find a time there weren't at least a few users lurking.