software updater problem

[Raymond House]

Hello all, I'm trying to upgrade to 13.04 from 12.10 but when I try to open
the software updater I get an error message,here it is: W:Failed to fetch
http://ppa.launchpad.net/duncanjdavis/download-monitor-submit/ubuntu/dists/quantal/main/source/Sources
404  Not Found
, W:Failed to fetch
http://ppa.launchpad.net/duncanjdavis/download-monitor-submit/ubuntu/dists/quantal/main/binary-i386/Packages
404  Not Found
, E:Some index files failed to download. They have been ignored, or old
ones used instead.    How can I get around this and do the upgrade ?  Thanks
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