I take some of Cookie's points, they're good.
But to properly clean this forum I'd estimate it would have to be closed for at least 3 days while repeated threads, etc were removed. General chit chat could be pruned as does forum and website need doing.
It's not that easy reading through every single post and trying to decide if you remove it will the topic make sence or not. It sounds easy but doesnt always work, trust me.