I was never able to get it working under IIS 5 properly. The built-in spider friendly links in 6.7 will "cheat" and use a query string for the Accelerator - ultimatebb.php?/ubb/forum/f/1 and the like. This is still friendly to most spiders, which stop only after seeing multiple arguments. (I.e. right now they'll browse ubb=forum, but not ubb=forum&f=1)