To answer your question about being able to overclock the processor, yes, you can. But, if your motherboard supports it.
The difference between locked and unlocked multipliers is that with unlocked multiplier, you go into BIOS, go to the correct setting, and change the multiplier--from x14 as this is a 2.8GHz chip (200MHz times 14 = 2.8GHz--200MHz being the base clock frequency) to anything you want it to up or down. AMD lists their processors with unlocked mulitpliers as "Black Edition." These make for very easy overclockers as you are taking the next whole or half number multiplier to run the chip faster than its default clock speed (Example: 2.8 = stock with 14 times multiplier. 14.5 times multiplier = 2.9 GHz; 15 times multiplier = 3.0 GHz; 15.5 = 3.1GHz; 16 = 3.2 GHz; etc...)
The locked multipliers are set and can't be changed. To overclock those, you must change the combination of: the base clock frequency, your RAM timings, and the HyperTransport speed, and voltages for cpu/ram/northbridge/southbridge
(depending upon the level of overclock you are looking for). It is a much more time consuming endeavor overclocking this way than by simply changing the multiplier.
Also, it is a risky endeavor either way. You shouldn't casually jump into overclocking your processor unless you read up first on what you're doing and the hazards associated, and unless you have the money to purchase new components in the event of a catastrophic failure (it can
(I would think that going the route of AMD's Overdrive
utility would lessen the risk of overclocking if that is what you're really trying to do)