Hi manabdeori
The idea is to install Chameleon on the drive you are booting from, then Chameleon will become the default bootloader and from there you can then load Windows7.
If you already have a Windows installation7 on the drive be careful when installing Chameleon's stage 0 booter (boot0) by making sure you don't use the standard version what ships with OS X. Instead, use the bundled fdisk in the i386 folder of the Chameleon binary files. This is because that version of fdisk will only write to the first 440 bytes of the MBR and won't destroy the existing Windows code. In the forth coming release of Chameleon RC5 this version of fdisk has been renamed fdisk440 to save confusion.
But note, before attempting this, it's wise to make sure you have a backup of your files and at least a recovery option available to you before proceeding, in case you do anything wrong.