How about retaining an archive of useful topics? Rather than editing out the first post whenever you solve your own questions, perhaps take 5 minutes to post a reply detailing what the problem was and how you went about fixing it; however simple the solution was.

No-one's going to be bothered if you post a topic saying, for example, "Hey I got this problem, x, y, z" with a reply 4 hours later "d'oh I misspelled the function name!" That's far better than dozens of topics with the first post being "Edit: Solved it".