The drive was almost completely full, nearly a full terabyte of TV shows had been recorded, so I went through the list of old shows to manually delete stuff.
I discovered that WMC had never deleted any of the Law & Order episodes that it had recorded. I had over a years worth of episodes filling up the drive! It had recorded not just the new episodes on NBC, but also the syndicated reruns on the local stations.
I started going through and deleting old episodes, which freed up almost half the drive. Nearly half a terabyte of Law & Order. Yikes! And I'm not really that big of a fan of the show.