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 !!!

Unfortunately, I experienced this issue after trying to install what appears to have been a corrupted Ubuntu 15.04 -- after install, it landed me in an OpenBox WM with much configuration broken. Additionally, my Windows 7 hard drive (seperate drive) somehow managed to get corrupted in the process.

In the windows CD repair-mode command prompt, issuing "bootrec /fixmbr" followed by "bootrec /fixboot" and then running Startup Repair from the Windows CD allowed me to get into the machine. However, my filesystem had been destroyed -- Steam, drivers, etc all corrupted. I'm amazed I was even able to log in.

Reinstalled. Windows first, then Ubuntu 14.04, no issues this time.