I've had a problem with Software Center for a few weeks, where it has just refused to delete a removed PPA from its "All Software" and "Installed Software" drop-down menus. I've tried many suggested solutions, none have worked, so I've finally decided to re-install Software Center if its possible. How do you do this and is it risky to your computer (i.e. will re-installing it cause all sorts of issues)?
You can reinstall the Software Center with a fresh start to all its systemwide configuration files by issuing this command in the Terminal (Ctrl+Alt+T):
sudo apt-get update; sudo apt-get --purge --reinstall install software-center software-properties-common software-properties-gtk
(You can copy that whole thing to the clipboard, paste it into the Terminal, and press enter. If you enter it manually--which I recommend against--then please take note to only press enter at the end; there is no line break in the middle, it's just too long to be displayed on one line.)
That command is written so that it also completely reinstalls the packages that provide the Software Sources window, which is at least as likely to be responsible for any problems relating to disabling a PPA as is the Software Center itself.