I don't think you have to have the Sony software installed to use Overdrive. (Someone please correct me if I'm wrong.) I believe ADE will see your Sony Reader when you plug it in and authorize it for you.
In the newest version of the Sony Software, there is an option that you can choose so that the software will not automatically run whenever you plug in your reader. I'm not at my computer with the Sony Reader software on it right now so can't tell you exactly where that option is, but it wasn't hard to find.
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