How do you reset the WHOLE database?

My computer crashed in the middle of my npc editing... When it rebooted and logged on there were no npc's. No trainers, no creatures, not nothing..
Can someone please guide me through how you are to reset the whole database?

Could you be more especific?

It seems that domin1 is referring to a World of Warcraft private server. My advice, domin1, post this question on the boards where you got your private server. They'll help you.