Bootcamp Broke My Mac!?!

I happened upon this thread recently all about a new pc game called C&C3. It sounded like fun, so I figured this was as good an opportunity as ever to test out Bootcamp on my new iMac 2.0 Core Duo. Well, I'm happy to report that windows works great on my mac, its faster than I've ever seen it run on a pc! But we seem to have a problem, I'm not prompted to pick which OS I want to run!?! At first I was terrified that I somehow managed to delete my entire mac partition, but this is not the case as I've installed a windows utility to 'show' mac drives and low and behold all my files are intact. So the million dollar question is, how can I rescue my OS X partition? As it stands, whenever I reboot the computer, I go straight to XP