Hello nidhish and welcome to Seven Forums.
When you say you have "backup CD" do you mean you created a set of restore disks when you got your Vaio? I have a Vaio VPCEB47GM and it took 4 DVDs (not CDs) to create the factory restore disks. Or is your backup cd something else?
If you actually created a set of factory restore DVDs, make sure your computer boots from the optical CD/DVD drive as first choice in the BIOS. Change Sony Vaio Boot Order
Insert DVD # 1 and restart your computer. Your Vaio will boot from the DVD. Follow the prompts to restore your machine to factory specs.
If you don't have a set of recovery DVDs you should still be able to restore your Vaio to factory specs by using the hidden recovery partition. Hidden Recovery Partition
There is a risk of data loss by using recovery disks or recovery partition. All data, settings, and programs added to the computer will be deleted. You should backup your data prior to restoring your machine to factory specs.