Do you still have the configured sources (i.e. you didn't delete the directory after you installed)? If so, try running "make uninstall". If that doesn't work, then you'll have to manually find all the files and delete them (you could try a "locate lame" and see what it returns).
Also, Fedora 7 is no longer supported, so you may like to consider upgrading to the newest version (which is 9).