How to dual boot Windows 7 and Windows XP with WIN7 preinstalled?

I am currently having windows 7 home premium. I wanted to run the C language and some other programs which don't run on 7. So i want to install windows XP sp3. I am having the installation cd. Before a month ago, I tried installing ubuntu but when I installed it, I lost my windows 7 and had to format the C: drive. Please tell me how do I install it so that I can use both OS.