Bootthink is a relatively new bootloader created by a Chinese hacker. However it sometimes be easier to use than the traditional Chameleon. This is what you have to do. One very interesting aspect is that you can install this onto a USB Drive. By doing that you experiment with different settings before you install to your real system, thus not taking any chance of screwing your system.
1. Get yourself a copy of Ideneb, IPC or iATKOS and burn it to disc.
2. Boot that up in your computer and goto Disk Utilities
3. Make 2 partitions, first Mac Extended, and 2nd partition use a FAT
4. Install OSX into the Mac Extended partition. (I would assume you already know how to do that, for any problems go to insanelymac and search first, if you cannot find what you are looking for ask nicely, they are really helpful.)
5. After your mac is booted and running smoothly, pop in the Windows 7 install Disc and boot with it.
6. Make sure you do not re-partition your drive, format it with NTFS, and click continue.
7. You can find windows 7 loader from google.
8. Download Boot-think(2.3.18 is the newest version at the time of this article) and install the windows version with the .exe and reboot. Make sure you run as administrator.
9. Boot into Windows 7 and goto "Darwin" folder. Once you are in there, goto the "MBR" folder, run "setupMBR.bat" as administrator.
It should already work.