Sorry if this question has been asked before, if there is can you post a link to that?
I tried overclocking my AMD Athlon II X2 270 to around 3.8GHz with the multiplier at x17 and the base clock (FSB???) at 215-220. Sometimes the system would not boot but say: "The previous oveclocking had failed!". In the BIOS I cannot change the CPU voltage; it is all set to AUTO and I cannot change that. My current stable overclocking is 3604MHz with the FSB at 212. Any more and the system would be very unstable and sometimes "AMD Radeon display driver stopped responding" message would appear after a system hang. So I reduced clock to 3.6 and it was ok. I think the reason why the overclockings failed was because I could not change the voltage. My motherboard is a MSI 760GM-P23.
AMD Athlon II X2 270
Stock cooler (although I can assure you that this is definitely not the cause)
Kingston 4GB (2x2GB) DDR3 1333 (sorry, I know nothing about timings etc)
MSI HD 7770