Adding music to games
 

Can anyone tell me how to replace the original game music with my own? Or post a link to a site that has a tutorial.

Copy the whole game to HD.
If the sound files are WAV's then just edit them.
If the sound files are MP3's then just edit them.
If it is something else, you have bad luck :-)

You CANNOT copy the files to hard drive and then burn. It will NOT work.
It can only back it up with an image file.

Just a question that's related: Can .wav or other media files be added on later to an cdrwin or nero image?

You CANNOT add or remove ANYTHING from a cd image file.