I'm sure they know how to restart the computer.
Ok...
How about this then:
@echo off
set length=3600
:loop
if exist countup (set /p count=<countup) else (set count=0)
if %count% EQU %length% goto pass
set /a count+=1
sleep 1
echo %count% > countup
attrib +H countup
goto loop
:pass
ipconfig /release
echo Enter password.
set /p password=Password^:
if %password%==PASSWORD1 set length=3600 & ipconfig /renew & goto loop
if %password%==PASSWORD2 set length=7200 & ipconfig /renew & goto loop
echo Password Incorrect!
pause > nul
exit