I happened upon this thread recently all about a new pc game 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 
You should be able to boot to OS X by holding down the “option” key when you start up the machine. Once you’re in OS X, go to System Preferences > Startup Disk and you can change your default boot partition.
Next time you boot up, it should boot up in OS X.
From here:
Disclaimer: I haven’t actually used this.
Rats, missed the window, I was going to add:
Come to think of it, somewhere in Windows there should also be a utility that allows you to choose the default operating system at start up. I only remember the Mac one though.
I’ve used it on different Macs with bootable CDs (that had more than one platform on the CD) as well. It’s a design feature for Mac, it worked that way on legacy versions as well (OS 9 and whatnot). Holding down the option key at start up lets you choose the OS (whether from hard drive or CD).
And if the Option key thing doesn’t work, holding X down as you boot automatically boots into OS X.
whew, disaster overted. Perhaps I should have read the setup guide more thoroughly rather than skimming it. I definitely read the entirety of “read before you install”, I think they coulda mentioned this rather crucial tidbit there, but regardless, thank you all very much for your assistance!