Can't access second partition on my HDD

This is because you installed them in the wrong order. I don't mean to sound preachy about that lol; but yeah, the way Vista's bootloader works, it has to be the last OS you install on your computer, and then you better hope the other OSes never f%*k up. You won't be able to reinstall them without them destroying Vista's new bootloader. Or they just won't be accessible anyway. Anyway, redo your installations with Vista first, or go ahead and install Vista again where you put it before. That should allow it to give you access to XP and still boot to itself.

Haha, well thanks a lot, both of you. I am currently re-installing them both in the right order. And I'm not rich or a pirate. I simply happened to have bought a retail copy of XP a long time ago which I then found out I didn't need, but kept around the house, and this copy of Vista I bought when I built this computer, but after being frustrated by trying to play older games on Vista, I've decided to dual boot and can now use this copy of XP.
Thanks again for all the help.

One of the better ways to run two different operating systems is to have a separate hard drive for each. This is not such a trick as it might sound for the motherboard Bios allows you to tell which hard drive to consider first. When you want to run the other OS just flip the Bios setting and go. On one of my machines there is Vista, XP Pro, and XP Pro64, all on different hard drives. Of course running SCSI alongside SATA and PATA (master) makes a bit of difference because each of them is distinct and not dependent upon the others in the chain. This also allows the DVD drives to remain on thier own (PATA slave) channel, thus not interfering with the disk access speeds.