how 2 get run and install once i've downloaded from lime?

[Vale]

Hi everyone! This is my first time at this so please forgive me if I'm screwing up. Anyhow, I just started using limewire today and i found some cool programs i'd like to share **** on my powerbook g4. I went and got a free download of stuffit Expander to open the files I download, but when I do try and open, I get NOTHING! I get an exe file that I guess my computer doesn't recognize. What I'm doing is simply double clicking on the application I just downloaded from limewire and this exe file pops out every time! What am I doing wrong? Can anyone help????
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