How do I turn off Overclocking??

[Will]

Well, you can do it on jumper-less MoBos, as long as the BIOS supports it. So the "jumpers" don't really have to be of the physical let's-stick-the-pLastic-connector-thingie-on-it variety, it could be part of the firmware.

But, like was already said, if you are asking about it, most likely your system is not overclocked, unless someone else did it for you (unlikely, since most people realize that there is only a small performance boost, and a shorter component lifetime when oc-ing).

You might want to take a look at some of the other causes to the issue, some games have problems with specific hardware.