If your Mac OS X Snow Leopard 10.6 have already been installed Rosetta, you can disable it via Terminal for higher performance and to prevent the system from running PowerPC apps
First, open the Terminal. Open Applications -> Utilities -> Terminal. Then type the following command from terminal and hit enter.
sudo sysctl -w kern.exec.archhandler.powerpc=/usr/libexec/oah/RosettaNonGrata
To re-enable it, try these commands:
sudo sysctl -w kern.exec.archhandler.powerpc=/usr/libexec/oah/translate