If you have unlocked BIOS, then you can do it, but Pentium D out of the box are really hot processors, and thus prone to overheating. Plus your mobo may not be made to release that much wattage with additional OC.
Must common way to OC is to raise the FSB just a notch, see if your machine is stable, you also have to adjust voltage at the same time. Any more questions, we will be gladly help ya out.
depends, can you change the values in your BIOS? Or is it locked???
Personally I would not bother overclocking that PC, the performance increase will be minimal and you can easily overheat the CPU if you do not know what you are doing.....
+1 for jsc + ovrclkr, a upgrade would be strongly recommended and the PD would produce alot of heat so getting a small oc, 5% would be even larger amount of heat