"Whose computer is this?"
これは誰(btw, the kanji for だれ isn't widely used, I don't think)のパソコンですか=is this who's computer?
It has a separate nuance and instead is trying to clarify that "this" is the computer belonging to "who". It also doesn't state what "this" これ is, so this means the speaker is asking if the object is "this" instead of its owner.
これはthis is誰のパソコンwho's computerですかquestion indicator
In this case, 誰の no longer means "whose". It's connected to a noun, so instead it means "who's". "Is this who's computer?"
このパソコンはthis computer is誰のwhoseですかquestion indicator
In this case, 誰の is left floating. "As for this computer, whose is it?"
I gave the same answer, and I also think DL is just refusing because they like us to translete the "This/That" literal (which is not naturel in my natural language so I get caught really often). I'd still like a confirmation that sentence makes sense in Japanese if you don't try to translate literally?
Both questions are asking the same thing (meaning-wise, anyway), but technically speaking, they are structured differently enough to have subtle differences to what the speaker is actually saying. "Whose computer is this?" is giving the information that there is an object ("this") and that it is a computer, while asking whose it is. "Whose is this computer?" is putting emphasis on "this computer" and has a silent call to ask everyone to inspect it, looking for differentiating details as it is apparently a very specific computer. Saying "this computer" automatically contrasts it to other computers, instead of focusing on the real question you're trying to ask, which is finding out to whom it belongs. It makes people wonder "what makes it different from other computers? What's so special or interesting about it?" It may be used in situations like, "This computer is Andrew's and this computer is Sally's, but whose is this computer?" See? It contrasts THIS computer to other computers. So, your teachers were right! It's very subtle, though, and either sentence is correct, depending on what you're trying to achieve.
As the object of the sentence is the computer we need to say This computer, this is why we mark このパソコン with the は particle. 誰の is the interrogative-possessive part of the sentence, you want to find out the to who the object belongs or exists (です) for, so it's not このですか but 誰のですか.
Also, この must be paired with a noun to make sense - otherwise we'd use これ so it wouldn't be directly attached to the noun. This unfortunately makes the このですか part wrong as it is a verb.
Although the given English is a natural way to ask the question, it is not in the natural order for Japanese as the "is" verb needs to go on the end. It would be closer if it said "This computer, whose is it?", which makes the order in Japanese make a lot more sense.
Hope this helps.
Pretty good explanation, except for a few things. "No" is not inquisitive, it's possessive. It connects the thing that is owned to the one owning it. In this case, "dare" or "who" is the one owning the thing, and the thing being owned is the PC. The "ka" at the end makes the sentence a question, and so is the inquisitive part. If you just said "kono pasokon wa dare no desu" it would sound weird what with "dare" being in there, but it's technically not a question due to the lack of "ka." Also, "wa" does not indicate the subject of a sentence, but the topic. This is a hard concept to grasp as an English-speaker since in English, the subject and the topic are always the same thing. So, the speaker of this sentence is bringing up a new topic, and this topic is the PC. Whether the subject of the sentence is the PC or whose it is may be up for debate. (This brings to mind the wa vs ga thing. "Watashi ga sensei desu." = "I am the teacher." (probably answering "Who is the teacher here?") vs "Watashi wa sensei desu." = "I am a teacher." (probably answering "What job do you have?"))
Someone please correct me if I've said anything erroneous. After all, I'm still a student, too.
Of course, this is technical sentence structure since I've seen a Japanese (nationality, not one who teaches the language) teacher hold up a hat amid her students and just ask "dare no?" (The equivalent of one of us holding up a hat and just shouting "Whose?" Simplistic, but the full, implied question gets across.) So, of course, in practice things will be a little different, but you need a mastery of the technical stuff before you reduce it like that.
Corrected my spelling and subject->object as 誰の is interrogative in nature as the の is simply making the interrogative into "whose" not "who".
I also wasn't explaining the か particle as that wasn't the thing being asked by @YufeiPang. If you've gotten this far you know what the question particle is. All they were asking was the difference in 誰の and この being swapped in the sentence.
I was just correcting technicalities, such as the claim that "no" was inquisitive by nature, while it's actually possessive by nature. Flaws in technical understanding can lead to a lot of confusion, especially when learning something as complex as a new language. It's important to be as exact as possible.
ありがとう！But I still have some questions. The second reason you mentioned does make sense. However, I don't understand why we have to say 'This computer' like このパソコン other than 'Computer of whom we have no idea' like 誰のパソコン. So I am wondering is 誰のパソコンはこれですか correct? Or as you mentioned(if I get it correctly), it has to have an interrogative before ですか. If this sentence is wrong, does it mean 誰の+noun can only serve as interrogative (誰のパソコンですか？) rather than object?
That doesn't sound correct to me.
You can use は alone to form questions, for example 私のパソコンは？means "What about my PC?" But by that logic, 誰のパソコンは？means "What about whose computer?" which is not what was asked here. (Besides, as the computer of "who" is not defined yet, I don't think using は makes sense either.)