For the purposes of the laptop, Slackware more than meets my needs. And I've noticed on my friend's laptop that running *nix gets better battery life out of his computer as opposed to XP.
So I'd have Windows partition a segment during install that would serve as C:\ for Windows. Once Windows is installed I would partition part of the unpartitioned drive and just have it NTFS? And then I'd install Linux on the remaining partition?
I haven't installed Linux in a while, but that's how it goes right? Or does Slackware require 2 partitions?
I was suggesting you use a distribution other than slackware, especially for a laptop. I'd recommend Fedora, Ubuntu, Debian, etc. One of the ones that has an officially maintained package repository. It makes updates so much easier, and installing new software is about as easy as it can be (usually). I'd steer clear of Slackware for a laptop... it's just way more trouble than it's worth for something like that. (imo).
Linux generally likes to have a swap partition, but it's a trivial amount of space if you're going to be using a 320GB hard drive. I think the swap partition on my desktop is only 5GB or something like that. It's generally easier to install Windows first, since you'll want to have grub (or something) on your MBR, and Windows overwrites the MBR every time it's installed. I'd give Windows most of the space (say 290 GB). You won't need much space for Linux if you're going to be putting files on the Winders partition.
Then, after you've installed Linux, you can just mount the Windows partition and use that as the 'shared' partition.
Also, I've liked Windows 7. It's worth checking out, anyway.