Here is a quick tool that I found for changing to and from the 32bit & 64bit kernel of OS X.
As we all know you can hold down the 6 & 4 keys while starting up, however this will only work with a wired keyboard.
This tool here will change that for you.
Small excerpt from the website --->
Should I use the 64-bit Kernel?
Benefits of K64
- 250% faster system call entry
- 70% faster user/kernel memory copy
Drawback of K64
The 64-bit Kernel can’t load 32-bit Kernel extensions. Therefore third-party software using kernel extensions that are not yet 64-bit won’t run correctly (you should contact the developers and ask for an update).
The good news is that most software do not use kernel extensions.
To sum up, you should use the 64-bit Kernel unless you need to run incompatible software.
If you locate any other useful tools to help with the iMac it would be cool if you posted them here. thanks
As we all know you can hold down the 6 & 4 keys while starting up, however this will only work with a wired keyboard.
This tool here will change that for you.

Code:
http://timesoftware.free.fr/k64enabler/K64Enabler.zip
Small excerpt from the website --->
Should I use the 64-bit Kernel?
Benefits of K64
- 250% faster system call entry
- 70% faster user/kernel memory copy
Drawback of K64
The 64-bit Kernel can’t load 32-bit Kernel extensions. Therefore third-party software using kernel extensions that are not yet 64-bit won’t run correctly (you should contact the developers and ask for an update).
The good news is that most software do not use kernel extensions.
To sum up, you should use the 64-bit Kernel unless you need to run incompatible software.
If you locate any other useful tools to help with the iMac it would be cool if you posted them here. thanks