Just modify the search function to select only topics where replycount = 0, shouldn't be all that difficult
Though there are a lot of people that post something, and then again asking if anyone is going to look at their code.
2 posts = 1 question + 1 reply = not shown in "Unanswered posts topic"
Then again, you could check to see if all the reply's in a topic have been done by the topic starter, and if so, still show that topic in the list. But maybe the 2nd post was to say that they solved the problem themselves, and thus you have 'Answered posts' among the 'Unanswererd posts'
Dilemma dilemma... :p