How to kill user process when have a runaway query??

Can anyone tell me how to identify and kill a user process that may involve a runaway query ? Is there a way to set up our userids so as to identify individual users on Server Manager ? Am very new to the DBA world and need much help. We are running Vers 7.1...... We are having performance problems and suspect that users may be rebooting their PC's when their response time is slow. Received on Sun Nov 05 1995 - 00:00:00 CET