I have purchased a dell labtop Dell Inspiron 15 3542 Laptop with Ubuntu Linux 12.04 installed in it.I want to install Win 8 on Ubuntu and have dual booting. I don't want to uninstall Ubuntu.How to do , pls guide me.
You may find it difficult because installing windows after ubuntu means you'll have the windows boot loader which is not capable of booting ubuntu. Usually people do Windows and then install ubuntu as the GRUB boot loader (i think that's what its called) which is installed with the ubuntu install allows you to boot ubuntu and windows.
I think what you'll have to do it create a partition and install windows, when you have windows running you'll need to install the linux boot loader over your windows boot loader.