Triple boot: Solved!!!
I have personally verified that this worked on my Macbook Pro 15 (2009)
Option 1: If you haven't upgraded to Lion
1. From one partition, install Bootcamp
2. Install Windows 7 (64-bit preferred)
3. Install a second Snow Leopard instance on a third partition
4. Upgrade the first Snow Leopard instance to Lion
Option 2: If you have upgraded to Lion and now lost the Windows 7 Bootcamp partition because you tried to install Snow Leopard in the third partition
1. Boot into Snow Leopard Install DVD and start Disk Utility (run Disk Utility in Snow Leopard might work as well)
2. Delete all partitions except the Lion partition
3. Create a new FAT32 partition (mimics a BootCamp partition)
4 Boot into Snow Leopard and run the BootCamp Assistant
5. Restore the hard drive into 1 Lion partition
6. Complete the steps for "Option 1"
What is the magic?
Bootcamp has a limitation of 4 partitions. People who tried Option 2 failed because they ended up with 5 partitions: EFI, Lion, Snow Leopard, Windows 7, and Lion Recovery. Adding the Snow Leopard partition before upgrading to Lion forces the Lion installer *not* to create the Lion Recovery partition.
Other tools I used:
- rEFIt to fix the MBR when Disk Utility seems to mess things up (DiskTest will probably work too)
- Winclone to back up my Windows 7 partition from my Snow Leopard partition
- SuperDuper or Carbon Copy Clone to back up my Lion/Snow Leopard partitions and boot from external hard drives