How can we delete a question I asked before at Stack Overflow, which has lots of up votes?
If I try to delete it, it shows this warning:
Sorry, this question cannot be deleted: too many existing answers, or upvoted/accepted answers
Your best option is to plead your case with the moderators - flag the question for moderator attention and write your reason for requesting deletion.
Obviously, it is reasonable to believe that the question will not be deleted exactly for the reasons the warning message conveys. However, if you plead your case with a moderator and the reasons for deletion are deemed acceptable, then a moderator can vote to have it deleted.
I viewed your questions on SO and I personally don't think you will have a lot of luck asking for them to be deleted. Even your closed questions (dupes or whatever) add some value to the site. Asking for them to be deleted just because you want to thin the number of questions asked will most likely not happen. In addition, any up-voted questions that get deleted will affect your rep score once a recalc has been performed.