Question: I had Windows 8 and Ubuntu on two different partitions. I was using both the operating systems as per my needs as I had dual booting options. I have now removed Windows 8 and installed Windows 7 in its place. Now when I start my laptop, I do not get an option to load Ubuntu. It directly enters Windows 7. 

How do I find out if my Ubuntu OS is safe?  

If so, how do I regain the Ubuntu OS?

Answer: 
You can check the following link for a tutorial to recover access to Ubuntu by reinstalling GRUB2: <https://help.ubuntu.com/community/Boot-Repair>

Basically, you will need to:

1. Boot Ubuntu from your live CD (or USB)
2. Install boot-repair:

```
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair

```
3. And finally, run boot-repair and clicking the "Recommended Repair" button.

Good luck!
No need of commands, use EasyBCD for adding grub again to boot menu.

1.Install windows 7 on a separate drive (Ubuntu previously installed on another drive)

After windows installation Ubuntu will not boot.
PC will boot into windows automatically.

2.Enter into windows and install EasyBCD for windows

3.Open EasyBCD and select add boot entry.
4.Select grub2
5.Give any name 
6.select drive to load.( give automatic or select the drive of your Ubuntu installation) 

7.OK and close EasyBCD.
8.done and reboot .

You can find new boot option and enter into it ,your grub is there.