Don't touch anything there!!!
The dot files in your home folder are your personal configuration and you can play with these as much as you want to without breaking the whole system, ou will only break what applies to you as a user. Don't meddle with global configurations if you don't undertand them.
So 1sf, I have no idea why firefox works for me and not for you. It must be karma
If you want to uninstall that media player, then if you kept the build directory, you should be able to enter it, su to root, then do
of course, if the developer didn't provide an unistall target in the makefile then you're stuffed. Trying to do it all by hand can be a real problem, it might just be best to leave it.
If you want a mdeia player, why not just use kaffeine (everything) or amarok (music)? And if you followed my tip about adding urpmi resources then installation will be as simple as typing (as root)
if they aren't already installed, which they probably are.