Selling a comp on ebay

I would simply reformat and leave it at that, If your sending the disk for windows, they can set it up as they want, if your not sending the disk, I would state that in the auction that the comp comes with NO OS. I would send as much as you have that came with the comp new, any extra batteries, extra drives if you have them, the power cord, etc. As far as software, I would include a listing on the auction of whats coming with it.