In order to set up dual-boot on your computer, I recommend creating a separate partition for each OS. There is also an option you change in Windows 2000/XP to boot multiple operating systems (go to Control Panel > System > Advanced > Startup and Recovery). There you can view all of your OS's and setup a menu so you can decide when your computer starts. Above all, MAKE SURE THAT YOUR OPERATING SYSTEMS ARE INSTALLED ON DIFFERENT VOLUMES. Otherwise, system files can easily be overwritten on one OS or the other, which is definitely not a good thing

. If you have any more questions, some of the guys here or on the IRC channels can help you out. I'm only on IRC on occasion, so just post here in the event that you can't get ahold of me another way.