if you have install a boot loader but you want go back to normal boot loader(because you have install the kali linux on other hardware.)
you can use easybcd, a good tool for windows  to rebuild the boot loader. but if the was an error can you can’t even get to the windows run your windows cd and select repair and find the command line then type bootrec and see the options.

bootrec /fixboot
bootrec scanos
bootrec rebuildbcd