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I think deleting a thread will be the most effective rather than closing a thread and move it to archival since as you said newbies here in forum will create the same thing over again and it always happens even there is a thread about it and also, mega spam threads just like in bitcoin and altcoin discussions with 40-100 pages of the same answer will make forum dirty so deleting them will make the forum cleaner and saves a lot of space.
Wanted to add some note, not every thread was deleted, some of them were locked.
I guess the reason why some of them got deleted was because it didn't have any value or another thread already existed talking about the same thing.
The one that got locked was because it has been answered/solved, or maybe being spammed a lot. Just a guess, though.