By installing Windows 7 after Linux Ubuntu, you will be unable to boot on it. Windows will have erased the boot loader called GRUB which contained the list of available operating systems. So we need to reinstall GRUB to get back access to Ubuntu and Windows. Simple handling that takes less than 5 minutes.
Step 1 — Create a live CD/USB from Ubuntu
This first step will allow us to have a live version of Ubuntu. In other words, we will be able to access the latter and proceed with the restoration of GRUB. This system will reside in RAM and has no connection to the inaccessible version of Ubuntu. You're following me?
To carry out this operation, please refer to tutorial Create a live USB from Ubuntu 11.10.
Step 2 — Reinstallation of the GRUB charger with Boot Repair
The second step is to start on your Ubuntu live.
To do this, insert your CD or USB stick and boot it. You may have to change a parameter in the BIOS. Often, just press F8 or F12 when booting and then select the DVD player or USB port.
Now we need to install a magic utility that will allow us to automatically solve the boot problem. Note that the installation is only virtual as nothing is registered on your hard drive.
To do this, open a Terminal then run the following command:
sudo add-apt-repository ppa:yannubuntu/boot-repair & & sudo apt-get update & & sudo apt-get install -y boot-repair
Press the button Entry when asked, then wait a few moments.
Once the operation is complete, enter boot in the Ubuntu search tool then launch Start-up repairer.
It is likely that you will be asked to update what to do by clicking on Yes.
Here we are finally ready to restore your boot. Just click on the button Recommended repair then let the software do.
If you wish, unwind the menu Advanced Options for a fine paramity.
Be careful to understand what you are doing in this particular case! To validate, do not forget to do Apply.
After the recovery operations are complete, restart the computer and then check that Windows is again in the list of available operating systems.
This solution deserves to be better known because it was difficult for me to find a clear and effective method of restoring the GRUB boot loader. This tutorial should make your life easier!