After downloading the ISO file it passed the hash check. Then I burned it and made my installation DVD for Windows 7 Ultima RTM. When I try to install it I get to about 20% complete then I get an error box saying that there are missing files. I tried both + and - DVD discs and still get the same error box. I thought I had a bad DVD burner, so I went and bought a new one - still does not work. I can still go back and install Windows Vista DVD. I did this about 20 times in two days. Any help would be very much appreciated.