Well. If you wanna restart you could always just give all your stuff away and start anew. There's no official feature for this though, and there's no way to delete accounts either. The account you have is the account you have to stick with. o:
Also you.. might wanna keep an eye on the dates of threads you post in. If a thread's last post was more than a month ago, it's against the rules to bring it up again unless you're the thread owner. Bringing up old threads that died in 2009 kind of floods the board and pushes down current ones, and the people who posted them often aren't even around anymore to see your question or reply in the first place.
It's generally a good idea to just stick with posting on threads that are already on the first page of the board.