if i change my pc case, does my HD, mobo, and other thing need to be formate or it will still be here and don need to be formated again.

If you change your case but use the same "innards" in the new case, then no, nothing needs to be done to the hard drive you can just put it into the new case along with all the other components.

Hengis is right. Nothing changes except the power supply, that most times comes with the new case. Your computer will not even notice this difference. I did a job like this a few days ago and there's really nothing to worry about.
Bluefish

Bluefish actually did it with me, ust bought a new X-Gear C888K case.....

If you change cases, nothing happens to the inner hardware, except maybe the Power Suply (depens on wether you use the old one, or the on you (option) got with the new case.

Just make sure the new power suply fits with the case, some older PSUs dont fit with newer Motherboards, but this shouldnt be a problem.

Good luck with your new case!!!

Thanks for your input Ruben!
For people who don't know, we're friends and spend time together building and fixing computer, just for explanation.

I'm going to mark this one as Answered by the way.

Bluefish