how do i change my macbook pro form 64 bit to 32 bit

Reboot your mac and hold down the keys "3" and "2" as soon as you hit the power button. Hold them down until you get to the login window. This will boot your computer using the 32bit kernel instead of the default 64bit one. For people that have older macs (late 2008 onward) if your mac supports 64bit (which it most likely will) you can hold down "6" and "4" instead and boot the 64bit kernel.

By using the keyboard combinations, it only boots into the desired mode that one time. It's not persistent. You'll have to use the combination each time you boot up. By using the terminal command, it will be persistent until you change it.

You can use the following terminal command to set the startup disk to use 32 bit...

sudo systemsetup -setkernelbootarchitecture i386

More info at:

http://support.apple.com/kb/ht3773

You can also open that App in 32 bits: Cmd + i over the application, then check the option "open in 32 bit".

Or just reverse whatever you did to make your MBP boot in 64-bit mode.

Snow Leopard only boots in 64-bit mode by default on Mac Pros.