If you can, put the second HDD on the secondary IDE cable. Look at your mb - next to the IDE connections you should find tiny letters identifying which is which. Sometimes it'll say "IDE1" next to the primary port and "IDE2" next to the secondary. Sometimes only #1 will be identified, cause after all the other one can only be #2. Then you'll want the 2 HDD's positioned and jumpered as primary on each IDE cable.
I hang around the Ubuntu Forums, and they've got some good step-by-step tutorials on dual-booting. Just do some searches.
It's important to note that you really want to have Windows installed first. People have tried it the other way & it's a hassle. Linux will modify the Master Boot Record (MBR) so that your PC will open to a DOS-looking screen that basically asks, "Which OS do you want to boot to?" Easy once it's set up.
You don't have to worry about drivers. Your Linux distro will either have them or not. For instance, if you try Ubuntu and it can't configure your wireless, you might try MEPIS, or PCLinux, or SUSE, or Mandrake. Since the device manufacturers (printers, cameras, scanners, video cards, what have you) typically don't bother to write drivers for Linux, you rely much more on the folks who built the Linux distro - if they didn't include the drivers you need for your printer or scanner or video card things get very complicated very quickly for those of us who can't write code.