Boot in with the W7 dvd run setup custom install, select partition to install to.
When windows 7 instalation completes it will setup a dual boot menu for you.
You will need to install all programs that you want to run in W7.
Run the compatability check. http://windows.microsoft.com/en-us/windows/downloads/upgrade-advisor
If you need more help >> http://www.sevenforums.com/tutorials/8057-dual-boot-installation-windows-7-xp.html