Windows Media Player

Windows Media Player is pissing me off... I seems to randomly decide to not allow me to seek through random video files (its works perfectly at other times), and doesn't seem to want to share my media with my XBOX 360. The latter function used to work, but now other devices don't even see this machine (though it sees them). Apparently it's related to Windows XP SP3, but nobody seems to be offering a proper solution.