Searching the site
Here's the quick run-down on searching the forum.
The search box that you see in the upper right hand corner searches whatever section you are currently viewing and below. In other words, if you are IN a thread, then that box searches only that thread. If you are at the board index, then it functions as a quick and simple way to search the entire forum. If, however, you really intend to search the entire forum, the better (more advanced) way is to either click the search button (in the blue nav bar, between HELP and PROFILE or the little magnifying glass next to the search box.
Both of those take you to the advanced search page. There, you can search not only by keywords or phrases, but narrow your search by member, post date, subjects only, by any number of boards, etc. You can also reorder the results by date, number of replies, etc.
The main thing to remember is, the search box at the top will not search the entire site UNLESS you are at the board index. If you're in a post, it searches only within that thread. Good luck, and happy searching!