I tried to search for this, but couldn't find results that explained what the "Overclock" option of the "Miscellaneous" option does? So out of curiosity: what does it do?
The Overclock option allows the CPU to use multipliers higher than the maximum default values.
Checking the Overclock box may not be necessary. It depends on the CPU and what speed you are trying to run it at. It should not hurt anything if you do decide to check Overclock.