Install a Grub, when your pc starts up, you'll be asked what OS would you like to use 1st.
Normally when you install ubuntu, Grub would be installed along with ubuntu, but if you don't get asked at the start up
which OS you would like to use and the PC starts up directly into ubuntu, open up the Terminal and do the following.
1. Grub will be installed
$ sudo grub
2. Grub Terminal will appear. Type in the following.
find /boot/grub/stage1
3. Whatever locations the find command found. Choose the one you want and type that number in where the ?'s are. ex. (hd0,1)
root (hd?,?)
4.
setup (hd0)
5.
quit
Then you are done.