well if you have a stock cooler, you can still over clock. Just remember the more you increase the voltages, the higher your temperatures will go. So if you plan on over clocking keep an eye on your temperatures. the following programs are very useful when overclocking:
1. your bios, don't over clock except through your bios
2. cpu-z will tell you what your current specs are
3. coretemp 0.95 will tell you the temperatures of your cores, and will tell you your Tjunction.
4. speedfan 2.33 will tell you temps, voltages
5. Everest will tell temperatures, voltages (compare with coretemp, speedfan)
6. orthos- run for 12hrs or more for stability. your core temps should not exceed 65c under load with small fft's