The wing wizard has spent more than a decade scorching down the wing with the Three Feathers on his chest and is Wales' all-time top try-scorer.
He has also made 13 appearances for the Lions during the 2009 and 2005 tours of South Africa and New Zealand, scoring eight tries in the process.
But Williams will retire from international duty following next month's showpiece tournament and he is determined to banish the painful memories of France 2007.
Four year's ago Wales crashed out of the global gathering with a shock 38-34 defeat to Fiji at the group stages.
Wales again face Fiji in this year's competition along with defending champions South Africa, World Cup bogey team Samoa and minnows Namibia.
But the Lion embarks on his third and final quest for global supremacy Williams is confident Wales have learned their lessons and ready for battle.
"Physically, we're in better shape than we've ever been as a Welsh side and we've learned from the mistakes of four years ago," said Williams.
"We've got a great squad that's capable of beating anyone. As well as being physically ready, we'll be mentally ready and perhaps that wasn't the case last time.
"Our first game is against the World Champions so we've got to prepare well.
"We have to play good rugby for 80 minutes rather than perhaps for 50 or 60 minutes because you'll come up short against the likes of Samoa and Fiji. It's going to be tough but we're confident that we can get through that pool."
Williams insists he still plans to bid farewell to international rugby following the conclusion of the World Cup but he reckons Wales have the players to fill his turbo-charged boots, in particular 2009 Lion Leigh Halfpenny and teen sensation George North.
"I'm as determined as ever to play in these games and to be successful," said Williams.
"I don't want to get too emotional on it being my last time wearing the shirt, but deep down I'll be thinking that.
"I want to go out to New Zealand, train well and make sure Warren Gatland find a it difficult not to pick me. When I play, I'll give it my all and that's all I'm thinking about at the moment.
"These youngsters coming through at the moment are playing like they've been playing for 10 years. I'm sure that George, Leigh and a few of the other guys will see a lot of World Cups.
"We've got a good blend of players in this squad. It's a strong squad and I think it's capable of big things."