How an I increase the recording space of my PVR? Can I add an external HD?
The PVR doesn't support an external hard drive.
The only way to increase recording space is to get a brand new PVR, but that will only help if your PVR has a smaller storage capability than the latest PVRs.
If you already have a PVR with the largest storage capacity, than it won't help to replace it with a newer one.
You can always try deleting old tv shows or movies that you won't be watching anymore to free up some space.