Changing back to Grub Legacy but getting an error

I was trying to change back to legacy Grub, but after rebooting it thrice, it was encountering an error.
The screen just say "Grub is loading" or some other errors then it will restart. I was not even allowed to choose the OS I want. It locked me out of the system. I am now planning to remove Ubuntu entirely and just retain Windows Vista, but I don't want to regret it later, so now, I am asking for anyone's help on how I can do this without encountering the error. By the way, the reason I'm trying to do this is because of the bootloader problem.
If there's anyone who knows how to remove the bootloader error, then that would be good as well, as I don't have to change back to legacy.Anyone knows how to do any of these

