Starting business

Hello all. I am an IT professional for over 10 years and now I am entering the world of entrepreneurship. The business that I want to get involved in is basic computer repair, network set-up. Basically geeksquad but cheaper. A concern that I have is the Operating Systems licensing. If I have a client that needs Windows re-installed and they do not have the CD how would that work. Do I have to pay huge fees to MSFT just to license Windows ? Also seeing how its going to be just me and a partner do you suggest becoming incorporated or an LLC ?

Thanks,

Michael