Intel and AMD rates their chips for a certain speed with a very cautious set of heat requirements. AMD marks their chips to 62c delta while Intel says 70c delta. That is not the same as the Temp that the CPU shows (its actually the temp on top of the processor).
Now both companies choose their speed based on less then ideal cooling. In some cases the cooling in some OEM machines is horrible, and they are made to run in 90f temps full out! So if you put on an good aftermarket cooler and a good case with good airflow you are exceeding Processor Specs.
With that said, You can Overclock safely... It takes skill, time, and often times allot of money (LOL)... Minor bumps are more then safe if your using the right cooling. Major bumps (4.5 ghz) can be safe for many years depending on the chip and really good cooling. Usually a chip that clocks to a max of 5ghz can run safely at 4.5
The OP never mentioned testing with Prime95... If he is not torture testing the processor, and can only get Microsoft Windows to load at a max of 4.5ghz then he needs to back down on the OCing. I would recommend that you do some major reading, and start going on forums that really specialize in Overclocking...
Many people (like me) overclock not because its easy or safe, but because it is fun! You learn so much about how the processor works, its weak points, voltage regulators, etc while overclocking.