It shouldn't. Gparted has a good help system with step-by-step instructions for creating, shrinking partitions. One "gotcha" is that Linux partitions must be unmounted before they can be altered, which is why the bootable cd is useful.
Edit: I don't use it, but I have read that Vista now has good software to shrink itself and create free space.
Last edited by sonoran; 19th August 2009 at 08:40 PM.