To reset password of 2970 Switch, power off the switch and press MODE button then power it on, take a look at the SYS led when it glows green leave the mode button. To recover the password click here.
Now your are in switch: prompt mode.
switch: dir flash:
switch: delete flash:config.text
switch: delete flash:vlan.dat
Now your switch has been reset, you can reconfigure the switch.