Why won't my LaCie Rikiki USB 2.0 hard drive work on my MacBook OS X?

Today I bought the LaCie Rikiki 500GB portable hard drive from my university. It’s interface is USB 2.0, and requires Mac OS X 10.5, 10.6. My MacBook is 10.7.2, so I’m wondering if I needed to buy the newest version of this hard drive (3.0) for it to be supported. So when I plug it in via the USB 2.0 cable, under my Finder > devices there is the tab called “LaCie Setup Assistant”. However, when I click on it is says “Launch of “LaCie Setup Assistant” failed: the PowerPC architecture is no longer supported.” And “You cannot open the application LaCie Setup Assistant because PowerPC Applications are no longer supported”.

This really frustrates me because I’m thinking that the guy at the Tech store sold me a product that is not supported on my MacBook Air even though he knew the version and memory capacity. Does anyone know if I can even use this on my MacBook? On the packaging it says it is compatible with Windows and Mac OS. Here is the link for the product on LaCie’s website.