Firefox vs. Widows Media Player?

Is there any known conflicts that would cause windows media player (v10.0) to stop working after installing Firefox (v1.0.4)? Maybe there is a mozilla media player I should start using?

When I double-click on my WMP icon, I simply get the “exclamation” sound, and nothing else happens.

I am working on a XP sp2 home PC, with 512Mb ram…any suggestions?