Ubuntu not detecting Windows 7 during dual boot installation

We often need to have multiple operating system installed in our machine.
I recently downloaded Ubuntu 14.04  and created a boot-able DVD with the .iso image on it. When I choose the DVD as the boot device it takes me to the Ubuntu installer GUI. However, once it gets to the actual installation step, it says "This computer currently has no detected operating system". But i have Windows 7 installed on my machine and its running properly.

Problem: Windows generally runs with Master Boot Record (MBR) partition ,bt sometime installation of some application leaves a Guid Partition Table (GPT) trace on the harddisk. And this GPT trace is the cause for Ubuntu not detecting Window.

In My case i have CentOS 6 on my Laptop, then i removed it and install Windows 7.Although Windows create its partion with MBR,but some GPT trace was there. So now its time for the

Solution:  Insert Ubuntu bootable DVD/ USB stick, proceed with you instalation with TRY Ubuntu ( this create a live Desktop session). Now Ubuntu 12 or above ships with GParted Utility, which you can start from command with sudo gparted

Then check you hard disk /dev/sda, it will show the disk label as GPT. Convert it to MSDOS with this utility.

Also,you can try from terminal with either one the following:

#check disk label or any GPT trace is there with fdisk

$sudo fdisk /dev/sda

# it will give warning about GPT trace disk label,Now execute the below steps to eliminate that trace.

$ sudo parted /dev/sda
$ mklabel msdos
$ quit


or

$ sudo apt-get install gdisk
$ sudo fixparts /dev/sda
and then press the key 'w'

Now proceed to install Ubuntu and it will be able to detect Windows.. :)