Belgiandip worm
 

I don't have it, but a friend of mine does.

Does anyone here know how to get rid of it?

Try AdAware with the latest reference file. The only reference I can find to anything with this name is a website , which is apparently some form of spyware/adware

also, the executable is apparently:
Windows\Sysytem32 \reduic.exe

Here's the problem.

Apparently this thing has taken over his Windows Media Player.
It completely screwed it up, so that every time that he tries to open it, it turns into this ad, and goes to this site.

Yea, that sounds like adaware, since the MP contains IE componenets...definitely try the anti-adware software, such as adaware, spybot, hijaack this.
After that, you may want to look at re-installing windows media player, or even upgrading to latest version.