Update GRUB
Try entering this command:
sudo update-grub
Use the Boot-Repair tool
For more information, see the Community Wiki page.
Installing Boot-Repair
Use the below commands to install:
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair && boot-repair
Launching Boot-Repair
- Use the launcher from the Dash...
... or ...
- Enter the command below in a terminal:
boot-repair
Other information
Thought this was worth mentioning...
DO NOT attempt to convert the disk from MBR to GPT form!!! That will
render Windows unbootable! (Yes, I know you're having trouble booting
Windows now, but the conversion would be like jumping into a swimming
pool filled with rusty nails in an effort to heal a scratch.) To give
an answer that's more than a guess, we need more information. Please
run the Boot Info Script, post the RESULTS.txt file it produces to a
pastebin site, and post the URL to your document here
– Rod Smith
Comment - "Windows 10 not booting after installing Ubuntu 15.04"