Hi,
To start... The System Repair Disk must be the same version or newer than the Image being restored, if you are trying to restore an image.. This may still apply if you are attempting some other type of repair..
Do you remember seeing a "EFI" partition on your HDD with Windows ? You can look in Disk Management and check if needed.. This partition is used on UEFI Bios machines, and not Legacy..
There is a remote possibility that your machine switched from a Legacy installation on Windows 7 to a UEFI installation on Windows 10... How you create the installation media for Windows 10, and how you boot with it, can trigger this..
Regardless... When you boot your computer with the CD, hit the key for BOOT OPTIONS at the manufacturer's screen... Usually F9, F11, F12, Esc, but it varies by machine..
You may see your CD\DVD drive listed twice.. as a CD\DVD Drive or Optical Drive, and again as a "UEFI CD\DVD Drive" or "UEFI Optical Drive"... Try both if they exist..
Some machines do not support booting from a "UEFI CD\DVD Drive"...
Just as a note... Windows 10 Installation Media has a "REPAIR" option on the lower left of the Install screen.. This gives all the same options and tools as the Repair CD would.. Simply select Repair... Troubleshoot...
If necessary, you should be able to boot with the UEFI USB Flash Drive version of the Installation Media..