Network Admin Password

I have volunteered to manage a computer lab located in a low income senior citizen housing community. The previous temp tech has left things in a mess. Several attempts to reach him have been futile. My plea for help is this…he has password protected several functions as the Network Admin. How would I be able to bypass, disable then reset password? To close to hacking? What are my alternatives? Reinstall OS?
By the way OS is Windows 98, 6 PCs plus server. Locked out of Control Panel, cannot Add/Remove programs or set display properties. Any and all advice welcome and appreciated.