This is an excellent question, and shame on me for not providing clear instructions for this
What you want to do is exit FARR, and then delete the FindAndRunRobot.ini file which will be in the "C:\Program Files\FindAndRunRobot" directory if you are on winxp or lower, or in MyDocuments\DonationCoder\FindAndRunRobot if on Vista or higher.
If you want a completely clean uninstall and reinstall, exit farr, then delete those two folders, and reinstall.