I may have a solution for you: The K-Lite Codec Pack

http://www.free-codecs.com/download/...Codec_Pack.htm

It's free - just download and install. Every so often you can download the latest one and it will update ALL of your codecs! I have it installed on any machine that I want to watch any videos on and it plays just about anything. It even includes Windows Media Player Classic (which can be run along side WMP, and has a few features that the newer versions don't).

I think GSpot is just a tool used to identify what codecs were used to encode the audio and video streams.

VLC is a free, portable media player, but it doesn't have many features. It's good if you just need a quick and dirty player for something but I don't know if I'd recommend it as a primary player. YMMV.