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!
You can also user Easybcd. You can have to download small application and you can recover your lost ubuntu partition. 

User below link for complete tutorial. .

<http://www.linuxbsdos.com/2012/03/10/restore-the-windows-bootloader-to-mbr-after-dual-booting-with-linux/>