Posted 14 May 2009 - 12:03 AM
Is your computer brand-built (Dell, HP, Gateway, etc.) or is it made with a custom motherboard? Most brand-build pcs cannot be overclocked easily.
Also, honestly, a pentium D already runs pretty hot, so I doubt that you could get much of an overclock on it without an extra heatsink. If your computer isn't too old, it might be worth changing your cpu for an E5200 or something for about 80$, it overclocks quite well and fits your socket, but you should check for motherboard compatibility first.