windows boot manager

I wanted to dual boot my windows 10 home desktop and install windows 7 on it. I made a new partition with no problem and followed instructions from u tube on how to install windows 7 from a cd. I went into BIOS, put boot from a cd on top, and restarted computer. Put in my windows 7 cd, typed in cd key when asked and let it run. It installed on the first step, and shut down before starting to copying windows files, when it restarted, I got a boot managers window that said a hardware/software change might have a file that is signed incorrectly or damaged. Another paragraph said to insert windows cd and click on repair computer, I don't have a cd for windows 10, my laptop and desktop are both running windows 10 and are about 2 years old, I don't beleive a cd was included with either one. At the bottom of Boot managers screen was File:\$windows~\windows\sys32\win/dad.efi. Status OXC0000428, and digitial signature could not be verified. How can I get rid of the boot managers window, and why didn't windows 7 install. My Windows 7 CD is from my old laptop and about 13 years old or so I think. I have wiped my old laptop clean several times and reinstalled windows 7 with no problem. Any help would be appreciated.

Thanks for the reply, but I want to install windows 7 on a windows 10 computer, not windows 10 onto windows 7.
Also I read or heard that the older versions of windows 7 wont work , that you have to buy a new key or cd from microsoft. I have wiped my old laptop clean several times and reinstalled windows 7 with no problem, so I don't know why I am having a problem with this. I am not computer savvy by any stretch of the imagination, but I can follow instructions. I even downloaded windows 7 instead of using cd, but could not get any response when I clicked on the exe. file. I thought the tutorial I watched on U Tube explained how to do this was pretty explicit, but like I said, no luck. How can I get rid of the boot managers window.