If you installed Windows after the Linux, and now your grub is not showing only Window is booting.
Just follow these simple commands you will get grub on your pc.
install grub 2

First of all insert your live Linux or Ubuntu CD/USB stick and select option live run.
When live version open then open Terminal (command line) and copy the following commands the Terminal

>> Latest version is Here

That's it.
Reboot your pc
Share To:
...