Thats not entirely true, though I have to advise against overclocking due to thermal limitations. Technically I've overclocked locked chips in the past by using setfsb to raise bclk. Ideally the bios method is best as you have alot more options on a bios that supports it. I do not think Dell has any such bios though. Could the psu handle it? More than likely a mild overclock is possible, could the factory cooling handle it? I'm going to venture a guess and say no. Can a bios unlock make it possible? Yes, but finding someone over at bios-mods to do this isnt going to be easy, and even then you need to know what you are doing before you start changing values. The fastest way to fry a cpu is to increase the voltage past your cooling's thermal budget and turn off features meant to keep the cpu safe. My advice to you is to find something meant to be overclocked and start putting in the man hours of research, start slow and work your way in. Ive overclocked just about one of everything over the last 17 years and it's easy to learn, difficult to master.You also need to know how to read falt codes/ stop errors when something does become unstable, but if you dont bluescreen, you arent pushing it.
In no way am I saying you should start overclocking this setup, you should start by researching and practicing with a setup thats meant to be overclocked.