WHS? Bought family pack cant run it on my Domain Controller???

So I thought I would just buy the family pack since I have about 8 machines running. So what I cant run WHS on my domain controller? What am I supposed to run that on? Can I run it on anything and have it control all the other clients?

Thanks

Since a DC runs on a server, you need a server version. Have a look at the Server Edition as well as the SBS suite