ok...
I have never really done this but it should work..
(1.)Get a Knoppix CD, and boot your computer with it
(2.)From the main Knoppix menu, find QTParted (Search for it if you want) and open it
(3.)Change the partition size for you main drive to about 20-30 GB so you get unpartitioned space. (if you have that much space) QTParted is free and comes with Knoppix. You will want some free, unpartitioned space if you want to keep your current windows install, because most Linux installers can't change your windows install's partition. When you have about 10 GB of unpartitioned space, go ahead and boot in your linux installer. At least in the Fedora Core 3 Install, you can choose, "Use free Space" inthe part for partitioning.
That *should* be it.
If you need more help, if you have ICQ or AIM you can instant message me at the ICQ address 265177680
And there is no need to worry; I'm online
(NOTE: Installing Linux, and partitioning can easily destroy your hard drive)