apt-get update won't update - undo /apt-add-repository

Question

When I run apt-get update, this happens:

Hit http://dl.google.com stable Release.gpg
Hit http://dl.google.com stable Release                                        
Hit http://security.debian.org wheezy/updates Release.gpg                      
Hit http://packages.crunchbang.org waldorf Release.gpg                         
Hit http://security.debian.org wheezy/updates Release                          
Ign http://ppa.launchpad.net wheezy Release.gpg                                
Hit http://packages.crunchbang.org waldorf Release                             
Hit http://dl.google.com stable/main i386 Packages                             
Ign http://ppa.launchpad.net wheezy Release                                    
Hit http://security.debian.org wheezy/updates/main i386 Packages               
Hit http://security.debian.org wheezy/updates/main Translation-en              
Hit http://packages.crunchbang.org waldorf/main i386 Packages                  
Hit http://http.debian.net wheezy Release.gpg                                  
Ign http://dl.google.com stable/main Translation-en_US               
Ign http://dl.google.com stable/main Translation-en                  
Hit http://http.debian.net wheezy Release                            
Hit http://http.debian.net wheezy/main i386 Packages                           
Hit http://http.debian.net wheezy/contrib i386 Packages                        
Ign http://packages.crunchbang.org waldorf/main Translation-en_US              
Hit http://http.debian.net wheezy/non-free i386 Packages                       
Ign http://packages.crunchbang.org waldorf/main Translation-en                 
Hit http://http.debian.net wheezy/contrib Translation-en             
Hit http://http.debian.net wheezy/main Translation-en                
Hit http://http.debian.net wheezy/non-free Translation-en
Err http://ppa.launchpad.net wheezy/main Sources
  404  Not Found
Err http://ppa.launchpad.net wheezy/main i386 Packages
  404  Not Found
Ign http://ppa.launchpad.net wheezy/main Translation-en_US
Ign http://ppa.launchpad.net wheezy/main Translation-en
W: Failed to fetch http://ppa.launchpad.net/glasen/intel-driver/ubuntu/dists/wheezy/main/source/Sources  404  Not Found

W: Failed to fetch http://ppa.launchpad.net/glasen/intel-driver/ubuntu/dists/wheezy/main/binary-i386/Packages  404  Not Found

E: Some index files failed to download. They have been ignored, or old ones used instead.

This has been caused by running apt-add-repository ppa:glasen/intel-driver. How can I undo what has happened from the previous command so that apt-get update works properly?

Note: This is on a Dell Dimension 3000

Solution

You just need to edit your sources. apt-add-repository simply adds a new deb line to the system's list of source repositories. These are stored as simple text files in /etc/apt/sources.list and /etc/apt/sources.list.d.

So, first find out where the offending repo is stored:

grep -F ppa.launchpad.net /etc/apt/sources.list /etc/apt/sources.list.d

This will return a list of files that contain the relevant line. For example:

/etc/apt/sources.list: deb http://ppa.launchpad.net/glasen/intel-driver/ ubuntu main

You can then open the listed file in your favorite editor (as root, sudo) and delete or comment out (add a # to the beginning of the line) the relevant lines.