I have Windows XP currently, and would like to install Linux purely for educational purposes on the same machine.
Currently I have two partitions, a 15 gig C drive that contains windows and program files, and a 60 gig partition , D, that contains stuff like mp3s and games.

My D partition has about 15 gigs free. Would it be possible to use maybe 10 of those gigs to install a version of Linux into? Would I have to completely repartition everything, or can I just use that space? Also, how does the dual boot work, does it automatically set itself up when I install Linux (I have Red Hat 9 on 3 CDs here), and allow me to choose the OS I want when I boot, or do I have to set something up myself? Thanks!

The free space will be enough for a linux system. No need to repartition all the disk. Dusring the installation process of the distro of your choice you'll get asked how you'd like to partition. There'll probably be a 'suggested partitioning scheme' you can adapt to your needs (the installation process will look at you disk, suggest a way to repartition it completely, another to use just the free space and a third option which will be labeled expert)

There's nothing very expert about the expert option anyway. You just need to know that for a linux installation the minimum requirment is a swap partition (2x Ram, more than 1GB not ususal) and a root (/) partition. To be on the safe side you might consider creating a /home partition as well (500MB if you're going to share your files with windows on the existing partition.

As for dual boot: the installation will ask you where you want to install the boot loader (GRUB). If you choose to install it on the MBR it will be the second thing you see after startup (after the 'inital bios screen(s)). The installation process will include an entry for your windows installation in this bootloader. Should you not be able to get into windows that way once you have installed you only need to insert your windows cd and from the command line type fixmbr (in XP) or fdisk /mbr (in win98) and you'll be back where you were.

Don't hesitate to ask if you have more specific questions and welcome to linux!!