Have you ever had this happen?
Your main OS is windows, and you just istalled a nux dualboot. But when you installed GRUB to the mbr, your windows loader got deleted! Hence you are not able to get into windows anymore... Sucks. But there's also a solution!
Boot into linux and fire up the terminal:
- sudo os-prober
- sudo update-grub
This will find your Windows partition and add it to GRUB so you can boot into it.
Simple as that.