I am not an overclocking person, but I have to say that today's motherboard are designed in a way that is safe to overclock them. If you do a screw up, it should automatically revert back to the previous settings, if the computer hangs up or becomes unstable.
Motherboards like Asus, they come with a buttom that will allow you to reset those changes, back to its defaults. Generally I would not recommend overclocking your system, but you should attempt at your risk, since overclock will void the warranty.
http://forums.guru3d.com/showthread.php?t=122731
http://www.overclockersclub.com/pages/overclock_faq/