First of all. I don't bother under or over clocking a system through the BIOS. This is possible and can yield desired results, however, it is much more unstable.

I use Linux, therefor, I have a nice tool already available to me. It's call cpufreq-selector. It is a command-line tool for choosing CPU frequency settings.

In order to find out if your system supports using this tool is to execute this command.
"cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies"

If you see a list of numbers, your systems supports setting the frequency at any of these speeds.

Executing this command,
"cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors"
will give you a list of modes that your system supports.

This allows you to set either the frequency or mode for your processor. Mode seems to mean the same as governor which seems to mean how it handles low and high loads.

Examples:
sudo cpufreq-selector -c 1 # Gives me one CPU
sudo cpufreq-selector -f 800000 # Sets my CPU frequency to 800,000 MHz
sudo cpufreq-selector -g powersave # Sets my governor to powersave

In addition to this. It turns out that you CAN do this without needing sudo.

To do this, execute "sudo dpkg-reconfigure gnome-applets" and answer "Yes" to the question regarding setting the suid of the cpufreq-selector executable.

Now you can just add the CPU Frequency Monitor Applet to your tray and play around.

As far as I can tell, using the settings in the files that you used cat on are 'safe' settings.