It's really easy to dual boot. Make sure you install Windows first though, or on a separate hard drive, because there's no guarantee it even recognizes the existence of partitions that aren't its own. After that, you'll want to:
* Make sure you have free space for a new partition.
* Get a Linux distribution (I use Debian; its installer wasn't too user friendly when I first installed it, but it's come a -long- way; I hear Ubuntu is very user-friendly, and it's also Debian-based).
* Install it on your new partition! When you do this, make sure to install something called "grub". Not LILO, grub.
* If grub wasn't installed yet, please install it at this time. You can make a bootable grub CD or floppy and install it / boot from there if you need to.
* Do the puppet master! At this point what you write in the grub configuration file in order to get Windows booting depends on what drive and partition Windows is on. (Windows doesn't like it if it's not on the first partition of the first drive, but grub has the ability to fool it to make it think it is -- if you need help with this, just PM me.)
* Install cool packages if the installer didn't do it already (if you're using Debian, now is the time). You'll at least want KDE, Firefox (Iceweasel in Debian), openoffice.org (alternatively; KOffice is great), xpdf (if you like viewing pdf files), xmms (if you like listening to music), pigeon (if you like IMing (formerly called gaim)).
If you're not hardcore and don't like editing files on the command-line with vi or emacs, kate is a great text editor for when you don't want to load up a full word processor like oo.org or koffice.
If you're a programmer or want to learn programming, you'll want (all debian package names):
* gcc (and pretty much all gcc packages, except like gnat or gfortran or whatever)
* libc6-dev and libstdc++-dev
* vim (or emacs if you happen to enjoy copious amounts of penis)
* make
Packages that you won't want to download from Debian right now but if you're a programmer you may want anyway include:
* Java (it's not packaged yet, but it's getting there -- get it from Red Hat or Sun right now).
* Eclipse (because of the status of Java).