Firstly, I would have normally considered myself rather computer literate, but apparantly not.

To begin with, my computer wasn't playing DVDs so when I called Dell they talked me through how to install k-Lite codec pack and this fixed the problem! My computer used to play DVDs fine but now, after installation of the codec pack, when my daughter is playing her Disney DVDs during songs the vocals are so quiet they're almost inaudible. During any other time of the film, the sound is fine. It's just during songs. Does anyone have any idea how to help me? Please! For my daughter's sake!

Thanks.

Look for setting called Dynamic range control or normalization. Also, make sure speaker configuration is
set properly for proper number of speakers hooked up to your PC i.e. vocals will be soft if using 5.1 sound since vocals are supposed to come out of centre channel.

If you are using Dolby AC3 filter for audio, try boosting gain or levels.