mce.ini is in /etc/mce/ (for future reference, (almost) all system configuration is in /etc/, and all user-specific configuration is in your home directory, usually in hidden folders (those starting with a ".", as in, /home/user/.gnome2/)
The file is commented somewhat, but it's still reasonably technical, so if you're not used to editing config files manually, you may want to ask someone else (maybe on IRC) for this specific issue. To edit it, you'll need root access, and the default command-line text editor is called vi.
Thus, the command:
rootsh vi /etc/mce/mce.ini
would open up the config file. Be warned, however, that vi is NOT newbie-friendly, and you probably won't have fun with it. If you install Leafpad, from the Extras repo, you should be able to launch that from the command line in a similar fashion (I think) and edit it in a graphical program.