Is there anyway you can install Microsoft Windows XP operating system on your PC? You have a 250 Gigabyte hard drive running Windows 7 and your hard drive isn't partitioned. Are you wanting to dual boot Windows XP and Windows 7 or are you wanting to remove Windows 7 and replace that with Windows XP?
What steps have you already tried? You want to dual boot both operating systems. You haven't tried anything yet as you do not want anything detrimental to happen to your PC.
You have vital information on it and you don't want to reformat or make PC recovery discs. It is possible to dual boot Windows XP and Windows 7 after Windows 7 was installed first. Please follow this How to Setup a Dual Boot Installation with Windows 7 and XP tutorial.
Skip to "Option Two" "When Windows 7 is First Installed".