i lost my dvd of system image window 7 home addition>>> how can i get a new system image on line wheni have the keys of my window .

Are you looking for installation disk or redoing a system image?

see How to Replace Microsoft Software. I assume you mean the installation DVD? I hope that helps. In the meantime, click Start>Help and Support>type system image in the search box. Then create a system image to an external usb hard drive.