MacWinIx

Recently, I went through the process of turning my MacBook Pro into a tri-booting system with 3 Operating Systems. I chose Mac OS X (10.6.4), Windows Vista Ultimate, and Linux (Ubuntu). It was a pain in the ass, but I finally got all 3 to at least function. I'm still working on Linux, but it is installed, and grub loads. The next thing to do, is to get past the Grub screen that comes up. I'm pretty sure I just need to tell it where the Kernel is, and which drive to use to boot, since I set up Mac OS X and Windows with Boot Camp.
The purpose of this post, is to help other users with tri-booting these Operating Systems, so long as you don't mind using a Wubi (Windows-based UBuntu Installer). I never did figure out a way to tri-boot without using Wubi and Windows to host Linux. If someone has, let me know! =]

1. Start up Mac OS X.
2. BACK UP ALL OF YOUR DATA! Either use Time Machine (which is a easy, fairly quick option that comes on Mac OS X standard) or some other backup software. If you are using a MacBook, it would be a good idea to get an external hard drive. I'm pretty sure you can't have more than one partition in a MacBook to start this process, as I've tried this many times. Perhaps I was just doing it wrong. Anyway...
3. Run Boot Camp and print (or email yourself) the Boot Camp Installation Instructions. After printing the instructions, you can continue with the prompts in Boot Camp. Determine the partition sizes for Mac OS X and Windows, but *keep in mind* that you will be installing Linux inside Windows, so include however much space you'd like Linux to use with the space you would give Windows.
4. Boot Camp will then tell you to restart your computer and insert the Windows CD/DVD that you have.
5. When the Windows CD starts, after completing the first few steps, it then shows the drive partitions that are inside your Mac. One is 200MB, one is whatever you set your Mac OS X partition to, and a Partition 3 (assuming you only had one partition when you started the process). You then delete the Partition 3, and it now appears as free space that you can select and choose the "New" option (under the advanced options of the drives) and select the default amount of space (which I believe is all of the space available).
6. Windows will then install, and you can let it set up normally.
7. Continue to follow the Boot Camp instructions. When it says to insert the Mac OS X Installation CD/DVD, OH NO! You can't! At least on a MacBook, because of the keyboard's built-in eject button. So, you'll have to restart the computer once you get to that point, and the trick here, is to hold down the "alt/option" key. Then select the "Macintosh" hard drive image, and then click the arrow below it. This will load Mac OS X, and allow you to eject the Windows installation disc. Do not restart your computer yet! Insert the Mac OS X Installation disc back into the drive, and then restart the computer. Again, hold down the "alt/option" key, and this time choose "Windows."
8. Continue to follow the Boot Camp instructions, and I'll let you read it off of those, I'm not going to write it all down... Maybe I'll upload them...
9. Now, if you've followed all of the instructions correctly, you can start Mac OS X, or Windows on your shiny Mac. Congratulations! However, this is only dual-booting, not tri-booting. Even though technically what I'm going to show you is a dual-boot in another dual-boot, I consider it a tri-boot.
10. Restart your computer, and choose the Windows partition. Then, log in to Windows with an Administrator account, or have an Admin nearby for administrative rights.
11. Run Windows Update, and update all of your software. Then restart your computer, and again, choose the Windows partition and log in.
12. Connect to the internet, and (since I used Ubuntu, which has a Wubi, that's what we'll use in this tutorial) download the Wubi installer, which you can run right off of your desktop.
13. Follow the instructions on Wubi. When it asks to set the partition size, this is why you included the Linux size in the Windows size in Boot Camp.

Once the installation process has completed, you're done! Well, mostly. I'll come back and finish this tutorial once I get Grub to load the Kernel and find the Linux root file system. Shouldn't be too hard right? Just gotta find the time to get it done. I hope this little tutorial has helped anyone looking to install Mac OS X, Windows, and Linux on the same Mac machine.