Windows 2000 Professional NT Reset or Restart?? How???

I need to reset my system and I really don’t know how. Can someone help asap? I inherited this Laptop from my grandfather and nobody can figure out his passwords. I need to either find a way to reset the password or completely reset the system! and I don’t know how to do either. It’s a dell and I don’t have any software, no reboot discs or running sys discs (ie Windows, 2000/xp/me etc…) Please help me.