The good news is that the E6600 is easily overclockable by just increasing the motherboard FSB. That cpu has a normal FSB of 266, and you should be able to bump it up to 400 (50% overclock), but do it in small jumps of 33 at first - 266->300->333->366->400. At each jump, run a benchmark program to be sure that everything is working as expected: 3DMark05 (or PCMark if video benchmarking is not critical). 50% is extremely good for any cpu, and you may be able to go higher, but as a beginner I would not recommend it. As Gary said, you need better cooling when you go higher. You also need to check if the SATA controller is affected by this. I have an MSI K8N Neo2 Platinum that I could only use certain SATA ports on because the other ones were not locked to the same frequency when the FSB was changed.