If it uses flash, reinstall Flash, if that doesn't work then tell me I'll give you a simple work around that'll fix flash movies from not loading.
If it uses Quicktime, install Quicktime or the Quicktime Alternative.
Other than that, it would be a problem with WMP, so try updating (or reinstalling) Window's Media Player.
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Now playing on Winamp:
Epica - Cry For The Moon
via
FoxyTunes