Follow the instructions at the link I posted
have a lot of old stuff transferred from Mac to Mac to Mac that is slowing down everything
If that included Power PC apps, read here > Lion upgrade questions and answers: Apple Support Communities
Well, for starters I don't hold the Apple Tech's opinion with very much regard. I see his comment to you as a cop out.
It has been my experience that have old software on a computer, as long as it is not running, is usually of little concern when it comes to performance.
A couple of much more likely culprits are the amount of free space on the system disk and how large you Desktop folder is.