The full gamut of options for bootrec, e.g. fixing the boot process of a Windows PC from the CD.

Boot with Windows 7/10 installation DVD, select repair and open a command prompt.

Type diskpart
Type select disk 0
Type list partition then note the partition number where you installed windows 7/10
Type select partition X   (X is the partition number where Windows is installed)
type active
type exit
type bcdboot c:\windows   (if C is your windows partition)