I just installed Ubuntu 14.04 flawlessly -- I'm happy with that.
But when after several restart, I realized something was missing from my grub: It was my windows boot option
How to make it appear again in my grub loader?
After you boot into Ubuntu 14.04, make sure you perform a complete system upgrade (sudo apt-get upgrade followed eventually by sudo apt-get dist-upgrade just in case you have heldback packages).
You can run previously mentioned commands and the next one in a terminal window (press Ctrl+Alt+T for the terminal window to pop-up). If there is no terminal emulator present on your system, you can install one using the Software Center and typing in as keyword terminal.
After you finish updating the system and reboot, you can run this command in the same terminal window:
See whether grub recognizes your Windows OS, and if it does you're good to go, I mean you done half the job for Windows to finally boot-up. Next you should repair your windows installation with your Windows DVD, using the Repair your computer option, and after you finish with this one, you can download Boot Repair CD iso image and burn it on a regular CD or put it on USB key via Unetbootin. I assume you're using Windows 7 ?
Next you should restart your computer with Boot Repair CD in tray and after it finishes loading you can choose the 'Recommended Repair' option to finally fix your dual-boot configuration and be able to boot into both Windows and Ubuntu.
If grub does not see your Windows OS after running sudo update-grub, it could be because you installed grub on the Ubuntu partition, and you should do the same steps, namely repair Windows mbr with your bootable Windows DVD, and then use Boot Repair CD to fix your boot problems.
Almost forgot to mention that you should download the 64bit iso image for Boot Repair CD if you're using a 64bit system, and the 32bit iso image if you're using a 32bit OS.
I am not sure but this video in the link below may help you. http://m.youtube.com/#/watch?list=PL99ADC865431A3C3E&v=_lL2xc1P8yM
I upgraded from 13.10 to 14.04 and lost Grub. I could boot into nothing and I could not fix it. I then used Gparted to erase everything (I had a triple boot setup Ubuntu/Win7/PC Linux O/S) and formatted to NTFS. I then reinstalled Windows with all updates and then Ubuntu 14.04 full install.... No Ubuntu. It boots into Windows and if Grub is there, it's ignoring it. I'm going to erase 14.04 and reinstall 13.10 but I don't hold out any hope that Grub will appear and I'm quite sure I'll be installing Windows and 13.10 again :-( This is a pain. I've never had this problem when upgrading before. I won't be using 14.04 anytime soon.