I am still new to dual booting OS, but as far as I can tell and from my experience, if you remove grub it messes up all your boots.
What I did was delete BT4 from my drive and when I tried to boot it didn't do anything, forgot what error it was giving me but so far I was locked out of my Windows OS since I deleted BT4. So then I needed to reformat and lost all my data on my Windows OS =/.




