I have a nec MA56H pld pc.Please teach me how to overclock this pc.there is not Bios feature and so jumpers.How to overclock this pc..please help me.

No bios features, no overclock... Save for upgrading or a faster PC

ditto.

And also, if you want to overclock, get some experience by building your own computer first. Which means no brand name PCs :D

setfsb, or clockgen. Only hopes.