That makes installing a new Operating System to be hard, because you need an USB containing the OS you want to install. That's the reason why we offer you A bootable USB.
A bootable USB makes easy to create a bootable USB drive containing the Operating system you need.
A Bootable USB allows you to create a bootable USB in order to install any Windows version (Vista, Seven or Server 2008). You only need the original DVD or the ISO file and a pendrive of, at least, 4GB.
Finally, we miss Windows XP support.
During the creation of the bootable USB, the program may seem to be frozen. Don't hurry up, it is still working.