# run Tor relay only my overnight when not deducted from my data allowance

my ISP limits me to 10Gb per month. I do not want Tor using this. However from midnight to 8 am the allowance is not affected so i could run a Tor relay. Editing my Windows XP torrc file C:\Documents and Settings\ianstx\Desktop\Tor Browser\Browser\TorBrowser\Data\Tor\torrc will start a relay but once 8 am arrives I will replace the torrc file with the torrc.orig file, but how can i stop the relay? do i need to [re]start a Tor browser or kill a process or service?