I installed Ubuntu alongside Windows 10, but when booting my laptop would automatically boot to Windows, so I used the installation USB to load Ubuntu and use the Boot-Repair program. However, doing this left my computer unable to boot either Windows or Ubuntu. It just lists some errors.
First thing I would try to do is check grub (purple screen where you choose which operating system to load) and try to make it work. Here is a solution for a similar problem. you can search the archive more (example). If grub doesn't work you can try, either repair windows or remove ubuntu (to install it later again). For this you have some tips here