Can I overclock a Pentium D on an Intel D945GTP motherboard?

Ive been overclocking Macs for years, but Ive just recently switched over to regular PC hardware/windows. So I just built this system with a Pentium D 820, Intel D945GTP motherboard, and Crucial PC5300 memory which apparently supports 3-3-3-12 timings and CAS 3.

When I overclocked G4s, generally all I had to do was change the CPUs multiplier (well I cooled better and a lot of the times boosted CPU core or external cache voltage). But someone told me that the Pentium D has a locked multiplier, meaning I cant overclock this system this way.

So first of all, without even being specific to my motherboard, how do you overclock a Pentium D? Im assuming you increase the FSB, but then does this affect memory speed, PCI speeds, or anything else that I dont particularly want overclocked? And, is this possible on my motherboard?

This is my first post here. Im sure you will all hear a lot more from me. Any help greatly appreciated.

Thanks

Chris Placzek