Scroll bars are an accepted GUI standard for MS Windows software. It is unprofessional to not include them in the interface and is a deterent when evaluating the software for purchase.
I am a professional programmer and know how easy it is to hook into the Windows scroll bars. I’ve read all of the reasons to NOT include them and don’t agree (especially when working on a laptop without a scroll wheel). If you want a more accessible product (and more sales), add the damn scroll bars. If you don’t like them, add a preference to turn them on and off.