If it's pre-built (e.g. Dell, Compaq, etc.) then they may have locked the BIOS. If you built it yourself, you haven't locked it, or if you did you'd definitely know. I personally don't know how to lock it. Anyways, different motherboards have different overclocking settings. Chances are, you can overclock just simply by raising the FSB (or whatever, I don't know what it is called for Intels). Just read that guide Trivium Nate posted, and you should be set.
Also, it would be a good idea to have software to monitor those temperatures. You probably shouldn't let them exceed 60*C, but I'm not exactly sure what the real limit is for Intels. I apologize for my limited knowledge of Intels. I'm mostly an AMD guy, but I am interested in the Conroe processors by Intel. Maybe I can sell my rig and get one, but I really don't see that happening.
The real reason that I even posted this is that I noticed something that looked odd in your CPU-Z picture. It stated that the voltage was "0.640V". That sounds abnormally low; anyone else notice that? Or are P4s supposed to run that low. If so, that's just crazy. You might also want to raise that if you can find out how (again, depends on the mobo) because most of the time it's good to raise the voltage when overclocking. Not a big raise; maybe .1 or .05V, but still a raise.
Good luck with your overclock. .2GHz should be easily obtainable.
