OK, slowly here. You are saying:
*You need a distro
*You need to dual boot
OK, so go to
http://distrowatch.com and find a distro you like. Download the ISOs and burn them as images to CD. Boot off the first CD, and follow the steps. The dualboot will be set up (using GRUB or LILO) during the install partitions.
You can use partition magic to resize the partitons if needed, otherwise the installer will either take care of it for you (which I don't trust) or tell you how to.