I find this old pc and it got P3 1000Mhtz and I thought of overlocking the Cpu . but am still noob on those stuffs and all the topics I could google is kinda for pro ppl ... any help .. step by step plz

Don't do it. Buy a new one.

its ok man . as I told you .. its not needed pc .. so i just want to test overlocking thing

The motherboard may not even allow you to overclock it, or the RAM may not be up to it. You're only going to get an extra 100Mhz or maybe 200Mhz anyway, just not worth it.

Overclocking is pretty technical as it is so I would just google around a bit more and read as much as you can. It just sounds difficult at first.

I find some tools that should overlock the cpu , but each time i use it the pc freez , I think I should stop here before someone get hurt XD

+1^^^ waste of time I think

many main board has accompany CD which normally come with driver and utility. I once had Gigabyte mainboard and CD which have utility to fine tune the clock of CPU/RAM.

I think that you should search for the utility come from the maker of your MB. That will reduce the risk to the MB.