O/C?

Okay, lets start off with OEM. OEM means Original Equipment Manufacturer. Buying something OEM is cheaper, but does not provide you with the necessary documentation over something that is bought retail. which is fine for Windows because most of use know how to install an OS one way or the other. A good example is when you buy an OEM CPU, all you get is the CPU, but buying the retail one will give you a cooler with the CPU. I do believe LG and LiteOn make good burners, just remember the cheap the crapper and the more chance you disk will come out broken. Overclocking gives you the chance to squeeze more performance out of your computer without upgrading. Before you make that call, what are the specs of your computer, RAM size, speed of the FSB, lets us know so we can help you. Sempron's should be good for overclocking, but I would have to have someone else answer that question since its not my skill area. For your GPU I recommend RivaTuner or ATITool depending on your card maker.