Just so all your bases are covered, if you cannot get to a gui, you can do this at the command line:
Q: How do I list my configured media sources?
A: urpmq --list-media
Q: How do I remove a source?
A: urpmi.removemedia <name>. The name can be a substring to match multiple
source names, like 'urpmi.removemedia cdrom' will remove all CD sources.
urpmi.removemedia -a will remove all sources
Above Q&A's extracted from this Urpmi FAQ:
http://speculation.org/garrick/urpmifaq.txt