If you don't know what "overclocking" means, then you haven't done it. If your PC starts to crash often, giving you the "blue screen of death", the simple fix is to re-install windows (I don't mean a full reformat, this is only neccessary if you have serious problems), and perform a full maintenance routine on the pc afterwards. I re-install windows on top of itself at least every six months or so, and keep up with proper maintenance. My pc never crashes since I began this routine.
Make sure both the cpu fan and the power supply fan are functioning correctly, and the case has clear airflow into and out of it. Most motherboards have the capability to monitor the temperature of the cpu, so you can determine if the crashes are heat-related or not.