Help to begin overclocking (BIOS Q)

Hi,

I have a Packard Bell iMedia 3720. (or has been known as iMedia D2521UK)
Windows 64bit
Intel Celeron E3300 2.5Ghz dual core
4GB DDR2 GEIL EVOONE pc2-6400
AMD Radeon HD 6670 1gb GDDR5 low profile
MOBO Packard Bell MCP73PV (Intel)
BIOS American Megatrends Inc. P01-A2, 09/24/2009

It seems that this CPU can handle a good boost, in some cases up to 4Ghz stably. I don't want/need to take it that high though.
I have read a lot about how to overclock and I know what to do and what not to do in regards to multipliers and voltage and FSB etc.
I already have many programs like CPU-ID, SpeedFan, RealTemp and Prime95.

My question is this;
I don't know where to start. I'm unsure if the motherboard has locked the Bios but I can;t seem to establish anywhere in the BIOS the options I would use to change the multiplier or FSB etc.

If it is not possible to do this utilizing the BIOS then is there a decent piece of software that can be used in windows?

Any help is greatly appreciated!

Thanks
Dan