Post originale di: tcagle53 ,
Here is a web article that gives a pretty complete rundown of how to do that correctly. https://www.itzgeek.com/how-tos/linux/ubuntu-how-tos/how-to-install-ubuntu-18-04-alongside-with-windows-10-or-8-in-dual-boot.html It sounds like you have damaged the UEFI boot for your windows. You will probably need to restore/reinstall win10 from either external media or from repair partition if your machine has a repair partition (most do that I’ve seen recently). If you have to reinstall windows and you also have important information on the machine you will need to get the information off of the HDD with a rescue bootable CD of some type (live linux cd most likely). Hope you have another device to research needed steps on the web in that case.