Lost Windows 7 in GRUB after installing Ubuntu 14.04

I just encountered the same problem after installing Kubuntu 14.04 on top of a (broken) 13.10. I found this tiny solution to recover the grub functionality:

Just open a terminal and enter

sudo update-grub

Booted from live USB with the version on my Ubuntu which is installed on my PC and installed Boot Repair by entering the following commands in terminal:

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo sed 's/trusty/saucy/g' -i /etc/apt/sources.list.d/yannubuntu-boot-repair-trusty.list
sudo apt-get update
sudo apt-get install -y boot-repair && (boot-repair &)

I've runned the Recommended repair, and followed the commands it gave me for terminal, and when it finished and restarted it still booted with Ubuntu only. Than I run Boot Repair again and after the program is done checking the problems, clicked on "Advanced options"-Boot Location tab. Bellow where there is a drop down menu against "OS to boot by default:" there was Ubuntu 14.04 and Windows 7, so I choose Windows 7 and than 'Apply'. When the process has finished I restarted and the GRUB now had the option to let me choose if want to boot with Ubuntu or Windows again. SOLVED

Hope it works for you as well !!!